21905951 has 4 divisors (see below), whose sum is σ = 22073304. Its totient is φ = 21738600.

The previous prime is 21905929. The next prime is 21905953. The reversal of 21905951 is 15950912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21905951 - 2²² = 17711647 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 (21905953) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83480 + ... + 83741.

It is an arithmetic number, because the mean of its divisors is an integer number (5518326).

Almost surely, 2^21905951 is an apocalyptic number.

21905951 is a deficient number, since it is larger than the sum of its proper divisors (167353).

21905951 is a wasteful number, since it uses less digits than its factorization.

21905951 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167352.

The product of its (nonzero) digits is 4050, while the sum is 32.

The square root of 21905951 is about 4680.3793649660. The cubic root of 21905951 is about 279.8040763743.

The spelling of 21905951 in words is "twenty-one million, nine hundred five thousand, nine hundred fifty-one".