1661518656 has 420 divisors, whose sum is σ = 5942234496. Its totient is φ = 457228800.

The previous prime is 1661518627. The next prime is 1661518657. The reversal of 1661518656 is 6568151661.

1661518656 is a `hidden beast` number, since 16 + 61 + 518 + 65 + 6 = 666.

It is a super-3 number, since 3×1661518656³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661518657) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 7874391 + ... + 7874601.

Almost surely, 2^1661518656 is an apocalyptic number.

1661518656 is a gapful number since it is divisible by the number (16) 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 1661518656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2971117248).

1661518656 is an abundant number, since it is smaller than the sum of its proper divisors (4280715840).

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

1661518656 is a wasteful number, since it uses less digits than its factorization.

1661518656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280 (or 254 counting only the distinct ones).

The product of its digits is 259200, while the sum is 45.

The square root of 1661518656 is about 40761.7302871210. The cubic root of 1661518656 is about 1184.4091141595.

The spelling of 1661518656 in words is "one billion, six hundred sixty-one million, five hundred eighteen thousand, six hundred fifty-six".