21079251 has 16 divisors (see below), whose sum is σ = 31332000. Its totient is φ = 14006304.

The previous prime is 21079243. The next prime is 21079271. The reversal of 21079251 is 15297012.

It is not a de Polignac number, because 21079251 - 2³ = 21079243 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21079271) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8305 + ... + 10541.

It is an arithmetic number, because the mean of its divisors is an integer number (1958250).

Almost surely, 2^21079251 is an apocalyptic number.

21079251 is a deficient number, since it is larger than the sum of its proper divisors (10252749).

21079251 is a wasteful number, since it uses less digits than its factorization.

21079251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2595 (or 2589 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21079251 is about 4591.2145451939. The cubic root of 21079251 is about 276.2390414905.

The spelling of 21079251 in words is "twenty-one million, seventy-nine thousand, two hundred fifty-one".