21667217 has 16 divisors (see below), whose sum is σ = 25593792. Its totient is φ = 18083520.

The previous prime is 21667211. The next prime is 21667223. The reversal of 21667217 is 71276612.

It is an interprime number because it is at equal distance from previous prime (21667211) and next prime (21667223).

It is not a de Polignac number, because 21667217 - 2⁶ = 21667153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21667211) 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, 39338 + ... + 39884.

It is an arithmetic number, because the mean of its divisors is an integer number (1599612).

Almost surely, 2^21667217 is an apocalyptic number.

It is an amenable number.

21667217 is a deficient number, since it is larger than the sum of its proper divisors (3926575).

21667217 is a wasteful number, since it uses less digits than its factorization.

21667217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 848.

The product of its digits is 7056, while the sum is 32.

The square root of 21667217 is about 4654.8057961638. The cubic root of 21667217 is about 278.7839139095.

The spelling of 21667217 in words is "twenty-one million, six hundred sixty-seven thousand, two hundred seventeen".