1661647680 has 672 divisors, whose sum is σ = 7303495680. Its totient is φ = 336752640.

The previous prime is 1661647583. The next prime is 1661647693. The reversal of 1661647680 is 867461661.

1661647680 is a `hidden beast` number, since 166 + 16 + 476 + 8 + 0 = 666.

1661647680 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (672).

It is a super-2 number, since 2×1661647680² = 5522146024898764800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 13083777 + ... + 13083903.

Almost surely, 2^1661647680 is an apocalyptic number.

1661647680 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1661647680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3651747840).

1661647680 is an abundant number, since it is smaller than the sum of its proper divisors (5641848000).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1661647680 is a wasteful number, since it uses less digits than its factorization.

1661647680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 227 (or 214 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The square root of 1661647680 is about 40763.3129173771. The cubic root of 1661647680 is about 1184.4397715033.

The spelling of 1661647680 in words is "one billion, six hundred sixty-one million, six hundred forty-seven thousand, six hundred eighty".