20577215921 has 4 divisors (see below), whose sum is σ = 20965465332. Its totient is φ = 20188966512.

The previous prime is 20577215891. The next prime is 20577215993. The reversal of 20577215921 is 12951277502.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16779575296 + 3797640625 = 129536^2 + 61625^2 .

It is a cyclic number.

It is not a de Polignac number, because 20577215921 - 2¹⁸ = 20576953777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20577215621) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 194124626 + ... + 194124731.

It is an arithmetic number, because the mean of its divisors is an integer number (5241366333).

Almost surely, 2^20577215921 is an apocalyptic number.

It is an amenable number.

20577215921 is a deficient number, since it is larger than the sum of its proper divisors (388249411).

20577215921 is an equidigital number, since it uses as much as digits as its factorization.

20577215921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388249410.

The product of its (nonzero) digits is 88200, while the sum is 41.

The spelling of 20577215921 in words is "twenty billion, five hundred seventy-seven million, two hundred fifteen thousand, nine hundred twenty-one".