21158457 has 16 divisors (see below), whose sum is σ = 29824320. Its totient is φ = 13305600.

The previous prime is 21158377. The next prime is 21158471. The reversal of 21158457 is 75485112.

It is not a de Polignac number, because 21158457 - 2⁷ = 21158329 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21158057) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15357 + ... + 16677.

It is an arithmetic number, because the mean of its divisors is an integer number (1864020).

Almost surely, 2^21158457 is an apocalyptic number.

It is an amenable number.

21158457 is a deficient number, since it is larger than the sum of its proper divisors (8665863).

21158457 is a wasteful number, since it uses less digits than its factorization.

21158457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1624.

The product of its digits is 11200, while the sum is 33.

The square root of 21158457 is about 4599.8322795511. The cubic root of 21158457 is about 276.5846015533.

The spelling of 21158457 in words is "twenty-one million, one hundred fifty-eight thousand, four hundred fifty-seven".