25391438921 has 4 divisors (see below), whose sum is σ = 25392212244. Its totient is φ = 25390665600.

The previous prime is 25391438857. The next prime is 25391438923. The reversal of 25391438921 is 12983419352.

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 20053675321 + 5337763600 = 141611^2 + 73060^2 .

It is a cyclic number.

It is not a de Polignac number, because 25391438921 - 2⁶ = 25391438857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25391438923) 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, 335120 + ... + 403841.

It is an arithmetic number, because the mean of its divisors is an integer number (6348053061).

Almost surely, 2^25391438921 is an apocalyptic number.

It is an amenable number.

25391438921 is a deficient number, since it is larger than the sum of its proper divisors (773323).

25391438921 is an equidigital number, since it uses as much as digits as its factorization.

25391438921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 773322.

The product of its digits is 466560, while the sum is 47.

The spelling of 25391438921 in words is "twenty-five billion, three hundred ninety-one million, four hundred thirty-eight thousand, nine hundred twenty-one".