21939917 has 8 divisors (see below), whose sum is σ = 22418880. Its totient is φ = 21464640.

The previous prime is 21939881. The next prime is 21939919. The reversal of 21939917 is 71993912.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21939917 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 (21939919) 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, 13448 + ... + 14990.

It is an arithmetic number, because the mean of its divisors is an integer number (2802360).

Almost surely, 2^21939917 is an apocalyptic number.

It is an amenable number.

21939917 is a deficient number, since it is larger than the sum of its proper divisors (478963).

21939917 is a wasteful number, since it uses less digits than its factorization.

21939917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1843.

The product of its digits is 30618, while the sum is 41.

The square root of 21939917 is about 4684.0065115241. The cubic root of 21939917 is about 279.9486172720.

The spelling of 21939917 in words is "twenty-one million, nine hundred thirty-nine thousand, nine hundred seventeen".