25640921 has 2 divisors, whose sum is σ = 25640922. Its totient is φ = 25640920.

The previous prime is 25640903. The next prime is 25640933. The reversal of 25640921 is 12904652.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17598025 + 8042896 = 4195^2 + 2836^2 .

It is a cyclic number.

It is not a de Polignac number, because 25640921 - 2¹⁰ = 25639897 is a prime.

It is not a weakly prime, because it can be changed into another prime (25640221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12820460 + 12820461.

It is an arithmetic number, because the mean of its divisors is an integer number (12820461).

Almost surely, 2^25640921 is an apocalyptic number.

It is an amenable number.

25640921 is a deficient number, since it is larger than the sum of its proper divisors (1).

25640921 is an equidigital number, since it uses as much as digits as its factorization.

25640921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 25640921 is about 5063.6865029344. The cubic root of 25640921 is about 294.8794719730.

The spelling of 25640921 in words is "twenty-five million, six hundred forty thousand, nine hundred twenty-one".