161771989520 has 40 divisors (see below), whose sum is σ = 379771544256. Its totient is φ = 64080551808.

The previous prime is 161771989507. The next prime is 161771989597. The reversal of 161771989520 is 25989177161.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

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, 9808022 + ... + 9824501.

Almost surely, 2^161771989520 is an apocalyptic number.

161771989520 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161771989520 is an abundant number, since it is smaller than the sum of its proper divisors (217999554736).

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

161771989520 is a wasteful number, since it uses less digits than its factorization.

161771989520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19632639 (or 19632633 counting only the distinct ones).

The product of its (nonzero) digits is 1905120, while the sum is 56.

The spelling of 161771989520 in words is "one hundred sixty-one billion, seven hundred seventy-one million, nine hundred eighty-nine thousand, five hundred twenty".