21479257 has 4 divisors (see below), whose sum is σ = 21884580. Its totient is φ = 21073936.

The previous prime is 21479251. The next prime is 21479281. The reversal of 21479257 is 75297412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6702921 + 14776336 = 2589^2 + 3844^2 .

It is a cyclic number.

It is not a de Polignac number, because 21479257 - 2¹⁵ = 21446489 is a prime.

It is a super-2 number, since 2×21479257² = 922716962544098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21479251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 202582 + ... + 202687.

It is an arithmetic number, because the mean of its divisors is an integer number (5471145).

Almost surely, 2^21479257 is an apocalyptic number.

It is an amenable number.

21479257 is a deficient number, since it is larger than the sum of its proper divisors (405323).

21479257 is an equidigital number, since it uses as much as digits as its factorization.

21479257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 405322.

The product of its digits is 35280, while the sum is 37.

The square root of 21479257 is about 4634.5719327679. The cubic root of 21479257 is about 277.9754347460.

It can be divided in two parts, 21479 and 257, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21479257 in words is "twenty-one million, four hundred seventy-nine thousand, two hundred fifty-seven".