20556964129 has 27 divisors (see below), whose sum is σ = 22901207979. Its totient is φ = 18444017280.

The previous prime is 20556964123. The next prime is 20556964147. The reversal of 20556964129 is 92146965502.

The square root of 20556964129 is 143377.

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

It can be written as a sum of positive squares in 13 ways, for example, as 12120909025 + 8436055104 = 110095^2 + 91848^2 .

It is not a de Polignac number, because 20556964129 - 2⁵ = 20556964097 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20556964123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 76419807 + ... + 76420075.

Almost surely, 2^20556964129 is an apocalyptic number.

20556964129 is the 143377-th square number.

20556964129 is the 71689-th centered octagonal number.

It is an amenable number.

20556964129 is a deficient number, since it is larger than the sum of its proper divisors (2344243850).

20556964129 is an frugal number, since it uses more digits than its factorization.

20556964129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 646 (or 323 counting only the distinct ones).

The product of its (nonzero) digits is 1166400, while the sum is 49.

Multiplying 20556964129 by its sum of digits (49), we get a square (1007291242321 = 1003639²).

The spelling of 20556964129 in words is "twenty billion, five hundred fifty-six million, nine hundred sixty-four thousand, one hundred twenty-nine".