21255939 has 12 divisors (see below), whose sum is σ = 31840536. Its totient is φ = 14170464.

The previous prime is 21255931. The next prime is 21255947. The reversal of 21255939 is 93955212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21255931) and next prime (21255947).

It is not a de Polignac number, because 21255939 - 2³ = 21255931 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21255931) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 43494 + ... + 43979.

It is an arithmetic number, because the mean of its divisors is an integer number (2653378).

Almost surely, 2^21255939 is an apocalyptic number.

21255939 is a deficient number, since it is larger than the sum of its proper divisors (10584597).

21255939 is an frugal number, since it uses more digits than its factorization.

21255939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87488 (or 87476 counting only the distinct ones).

The product of its digits is 24300, while the sum is 36.

The square root of 21255939 is about 4610.4163586383. The cubic root of 21255939 is about 277.0087143796.

The spelling of 21255939 in words is "twenty-one million, two hundred fifty-five thousand, nine hundred thirty-nine".