6551864434921 has 81 divisors (see below), whose sum is σ = 7697798423397. Its totient is φ = 5573098702080.

The previous prime is 6551864434891. The next prime is 6551864434937. The reversal of 6551864434921 is 1294344681556.

The square root of 6551864434921 is 2559661.

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

It can be written as a sum of positive squares in 4 ways, for example, as 104144971225 + 6447719463696 = 322715^2 + 2539236^2 .

It is not a de Polignac number, because 6551864434921 - 2⁷ = 6551864434793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6551864434121) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 27186159361 + ... + 27186159601.

It is an arithmetic number, because the mean of its divisors is an integer number (95034548437).

Almost surely, 2^{6551864434921} is an apocalyptic number.

6551864434921 is the 2559661-st square number.

6551864434921 is the 1279831-st centered octagonal number.

It is an amenable number.

6551864434921 is a deficient number, since it is larger than the sum of its proper divisors (1145933988476).

6551864434921 is an equidigital number, since it uses as much as digits as its factorization.

6551864434921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 632 (or 316 counting only the distinct ones).

The product of its digits is 24883200, while the sum is 58.

The spelling of 6551864434921 in words is "six trillion, five hundred fifty-one billion, eight hundred sixty-four million, four hundred thirty-four thousand, nine hundred twenty-one".