21158657 has 8 divisors (see below), whose sum is σ = 22829184. Its totient is φ = 19494288.

The previous prime is 21158633. The next prime is 21158671. The reversal of 21158657 is 75685112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21158657 - 2¹⁴ = 21142273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21158677) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7688 + ... + 10070.

It is an arithmetic number, because the mean of its divisors is an integer number (2853648).

Almost surely, 2^21158657 is an apocalyptic number.

It is an amenable number.

21158657 is a deficient number, since it is larger than the sum of its proper divisors (1670527).

21158657 is a wasteful number, since it uses less digits than its factorization.

21158657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3079.

The product of its digits is 16800, while the sum is 35.

The square root of 21158657 is about 4599.8540194228. The cubic root of 21158657 is about 276.5854730212.

The spelling of 21158657 in words is "twenty-one million, one hundred fifty-eight thousand, six hundred fifty-seven".