21025439 has 2 divisors, whose sum is σ = 21025440. Its totient is φ = 21025438.

The previous prime is 21025423. The next prime is 21025469. The reversal of 21025439 is 93452012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21025439 - 2⁴ = 21025423 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21025469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10512719 + 10512720.

It is an arithmetic number, because the mean of its divisors is an integer number (10512720).

Almost surely, 2^21025439 is an apocalyptic number.

21025439 is a deficient number, since it is larger than the sum of its proper divisors (1).

21025439 is an equidigital number, since it uses as much as digits as its factorization.

21025439 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 21025439 is about 4585.3504773354. The cubic root of 21025439 is about 276.0037762908.

The spelling of 21025439 in words is "twenty-one million, twenty-five thousand, four hundred thirty-nine".