1661640920 has 32 divisors (see below), whose sum is σ = 3859297920. Its totient is φ = 643215360.

The previous prime is 1661640917. The next prime is 1661640923. The reversal of 1661640920 is 290461661.

It is an interprime number because it is at equal distance from previous prime (1661640917) and next prime (1661640923).

It is a super-2 number, since 2×1661640920² = 5522101094036892800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661640923) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 668777 + ... + 671256.

It is an arithmetic number, because the mean of its divisors is an integer number (120603060).

Almost surely, 2^1661640920 is an apocalyptic number.

1661640920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1661640920 is an abundant number, since it is smaller than the sum of its proper divisors (2197657000).

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

1661640920 is a wasteful number, since it uses less digits than its factorization.

1661640920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1340075 (or 1340071 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 1661640920 is about 40763.2299995965. The cubic root of 1661640920 is about 1184.4381653017.

The spelling of 1661640920 in words is "one billion, six hundred sixty-one million, six hundred forty thousand, nine hundred twenty".