161640640 has 56 divisors (see below), whose sum is σ = 439899552. Its totient is φ = 55418880.

The previous prime is 161640631. The next prime is 161640653. The reversal of 161640640 is 46046161.

It is a tau number, because it is divible by the number of its divisors (56).

It is a super-2 number, since 2×161640640² = 52255392999219200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 161640599 and 161640608.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33841 + ... + 38320.

Almost surely, 2^161640640 is an apocalyptic number.

161640640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161640640 is an abundant number, since it is smaller than the sum of its proper divisors (278258912).

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

161640640 is an equidigital number, since it uses as much as digits as its factorization.

161640640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72185 (or 72175 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 161640640 is about 12713.7972297815. The cubic root of 161640640 is about 544.7327927285.

The spelling of 161640640 in words is "one hundred sixty-one million, six hundred forty thousand, six hundred forty".