21965121 has 32 divisors (see below), whose sum is σ = 35020800. Its totient is φ = 13562640.

The previous prime is 21965117. The next prime is 21965149. The reversal of 21965121 is 12156912.

21965121 is a `hidden beast` number, since 2 + 1 + 9 + 651 + 2 + 1 = 666.

It is not a de Polignac number, because 21965121 - 2² = 21965117 is a prime.

It is a super-3 number, since 3×21965121³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21965101) 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 31 ways as a sum of consecutive naturals, for example, 23656 + ... + 24566.

It is an arithmetic number, because the mean of its divisors is an integer number (1094400).

Almost surely, 2^21965121 is an apocalyptic number.

It is an amenable number.

21965121 is a deficient number, since it is larger than the sum of its proper divisors (13055679).

21965121 is a wasteful number, since it uses less digits than its factorization.

21965121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 986 (or 980 counting only the distinct ones).

The product of its digits is 1080, while the sum is 27.

The square root of 21965121 is about 4686.6961710783. The cubic root of 21965121 is about 280.0557754535.

The spelling of 21965121 in words is "twenty-one million, nine hundred sixty-five thousand, one hundred twenty-one".