21651172 has 6 divisors (see below), whose sum is σ = 37889558. Its totient is φ = 10825584.

The previous prime is 21651167. The next prime is 21651173. The reversal of 21651172 is 27115612.

It can be written as a sum of positive squares in only one way, i.e., 20848356 + 802816 = 4566^2 + 896^2 .

It is not an unprimeable number, because it can be changed into a prime (21651173) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2706393 + ... + 2706400.

Almost surely, 2^21651172 is an apocalyptic number.

It is an amenable number.

21651172 is a deficient number, since it is larger than the sum of its proper divisors (16238386).

21651172 is a wasteful number, since it uses less digits than its factorization.

21651172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5412797 (or 5412795 counting only the distinct ones).

The product of its digits is 840, while the sum is 25.

The square root of 21651172 is about 4653.0819893915. The cubic root of 21651172 is about 278.7150819272.

Adding to 21651172 its reverse (27115612), we get a palindrome (48766784).

The spelling of 21651172 in words is "twenty-one million, six hundred fifty-one thousand, one hundred seventy-two".