21658161 has 16 divisors (see below), whose sum is σ = 33139584. Its totient is φ = 12324864.

The previous prime is 21658159. The next prime is 21658163. The reversal of 21658161 is 16185612.

It is an interprime number because it is at equal distance from previous prime (21658159) and next prime (21658163).

It is not a de Polignac number, because 21658161 - 2¹ = 21658159 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (21658163) 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, 3391 + ... + 7403.

It is an arithmetic number, because the mean of its divisors is an integer number (2071224).

Almost surely, 2^21658161 is an apocalyptic number.

21658161 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21658161 is a deficient number, since it is larger than the sum of its proper divisors (11481423).

21658161 is a wasteful number, since it uses less digits than its factorization.

21658161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4280.

The product of its digits is 2880, while the sum is 30.

The square root of 21658161 is about 4653.8329364084. The cubic root of 21658161 is about 278.7450684509.

The spelling of 21658161 in words is "twenty-one million, six hundred fifty-eight thousand, one hundred sixty-one".