21261951 has 12 divisors (see below), whose sum is σ = 32518512. Its totient is φ = 13340736.

The previous prime is 21261943. The next prime is 21261953. The reversal of 21261951 is 15916212.

It is not a de Polignac number, because 21261951 - 2³ = 21261943 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21261953) 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, 69331 + ... + 69636.

It is an arithmetic number, because the mean of its divisors is an integer number (2709876).

Almost surely, 2^21261951 is an apocalyptic number.

21261951 is a deficient number, since it is larger than the sum of its proper divisors (11256561).

21261951 is a wasteful number, since it uses less digits than its factorization.

21261951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138990 (or 138987 counting only the distinct ones).

The product of its digits is 1080, while the sum is 27.

The square root of 21261951 is about 4611.0683143931. The cubic root of 21261951 is about 277.0348281699.

The spelling of 21261951 in words is "twenty-one million, two hundred sixty-one thousand, nine hundred fifty-one".