21293217 has 18 divisors (see below), whose sum is σ = 33808866. Its totient is φ = 12904320.

The previous prime is 21293191. The next prime is 21293257. The reversal of 21293217 is 71239212.

It can be written as a sum of positive squares in only one way, i.e., 20439441 + 853776 = 4521^2 + 924^2 .

It is not a de Polignac number, because 21293217 - 2⁷ = 21293089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21293257) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 8688 + ... + 10865.

Almost surely, 2^21293217 is an apocalyptic number.

It is an amenable number.

21293217 is a deficient number, since it is larger than the sum of its proper divisors (12515649).

21293217 is a wasteful number, since it uses less digits than its factorization.

21293217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19581 (or 19567 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 21293217 is about 4614.4573895530. The cubic root of 21293217 is about 277.1705562075.

The spelling of 21293217 in words is "twenty-one million, two hundred ninety-three thousand, two hundred seventeen".