21645177129 has 21 divisors (see below), whose sum is σ = 32458876743. Its totient is φ = 14427469872.

The previous prime is 21645177097. The next prime is 21645177139. The reversal of 21645177129 is 92177154612.

The square root of 21645177129 is 147123.

It is a perfect power (a square), and thus also a powerful number.

21645177129 is a `hidden beast` number, since 2 + 1 + 6 + 4 + 517 + 7 + 129 = 666.

It can be written as a sum of positive squares in only one way, i.e., 2235114729 + 19410062400 = 47277^2 + 139320^2 .

It is not a de Polignac number, because 21645177129 - 2⁵ = 21645177097 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21645177139) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 3969597 + ... + 3975045.

Almost surely, 2^21645177129 is an apocalyptic number.

21645177129 is the 147123-rd square number.

21645177129 is the 73562-nd centered octagonal number.

It is an amenable number.

21645177129 is a deficient number, since it is larger than the sum of its proper divisors (10813699614).

21645177129 is an frugal number, since it uses more digits than its factorization.

21645177129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10916 (or 5452 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The spelling of 21645177129 in words is "twenty-one billion, six hundred forty-five million, one hundred seventy-seven thousand, one hundred twenty-nine".