21912517 has 8 divisors (see below), whose sum is σ = 24242112. Its totient is φ = 19639200.

The previous prime is 21912511. The next prime is 21912521. The reversal of 21912517 is 71521912.

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 21912517 - 2³ = 21912509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21912511) 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, 13248 + ... + 14809.

It is an arithmetic number, because the mean of its divisors is an integer number (3030264).

Almost surely, 2^21912517 is an apocalyptic number.

It is an amenable number.

21912517 is a deficient number, since it is larger than the sum of its proper divisors (2329595).

21912517 is a wasteful number, since it uses less digits than its factorization.

21912517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28139.

The product of its digits is 1260, while the sum is 28.

The square root of 21912517 is about 4681.0807512796. The cubic root of 21912517 is about 279.8320293574.

The spelling of 21912517 in words is "twenty-one million, nine hundred twelve thousand, five hundred seventeen".