21710239 has 2 divisors, whose sum is σ = 21710240. Its totient is φ = 21710238.

The previous prime is 21710209. The next prime is 21710251. The reversal of 21710239 is 93201712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21710239 - 2⁷ = 21710111 is a prime.

It is equal to p_1372057 and since 21710239 and 1372057 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21710209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10855119 + 10855120.

It is an arithmetic number, because the mean of its divisors is an integer number (10855120).

Almost surely, 2^21710239 is an apocalyptic number.

21710239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21710239 is an equidigital number, since it uses as much as digits as its factorization.

21710239 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21710239 is about 4659.4247499021. The cubic root of 21710239 is about 278.9683078727.

The spelling of 21710239 in words is "twenty-one million, seven hundred ten thousand, two hundred thirty-nine".