21708951 has 16 divisors (see below), whose sum is σ = 31667328. Its totient is φ = 13119200.

The previous prime is 21708943. The next prime is 21708979. The reversal of 21708951 is 15980712.

It is a cyclic number.

It is not a de Polignac number, because 21708951 - 2³ = 21708943 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21708901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14500 + ... + 15926.

It is an arithmetic number, because the mean of its divisors is an integer number (1979208).

Almost surely, 2^21708951 is an apocalyptic number.

21708951 is a deficient number, since it is larger than the sum of its proper divisors (9958377).

21708951 is a wasteful number, since it uses less digits than its factorization.

21708951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1902.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21708951 is about 4659.2865333654. The cubic root of 21708951 is about 278.9627909937.

The spelling of 21708951 in words is "twenty-one million, seven hundred eight thousand, nine hundred fifty-one".