25645911821 has 4 divisors (see below), whose sum is σ = 25646682144. Its totient is φ = 25645141500.

The previous prime is 25645911793. The next prime is 25645911859. The reversal of 25645911821 is 12811954652.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 25645911821 - 2²⁶ = 25578802957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25645910821) 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, 332855 + ... + 402596.

It is an arithmetic number, because the mean of its divisors is an integer number (6411670536).

Almost surely, 2^25645911821 is an apocalyptic number.

It is an amenable number.

25645911821 is a deficient number, since it is larger than the sum of its proper divisors (770323).

25645911821 is an equidigital number, since it uses as much as digits as its factorization.

25645911821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 770322.

The product of its digits is 172800, while the sum is 44.

The spelling of 25645911821 in words is "twenty-five billion, six hundred forty-five million, nine hundred eleven thousand, eight hundred twenty-one".