21521992 has 8 divisors (see below), whose sum is σ = 40353750. Its totient is φ = 10760992.

The previous prime is 21521987. The next prime is 21521999. The reversal of 21521992 is 29912512.

It can be written as a sum of positive squares in only one way, i.e., 19131876 + 2390116 = 4374^2 + 1546^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×21521992² = 926392279296128, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21521999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1345117 + ... + 1345132.

Almost surely, 2^21521992 is an apocalyptic number.

It is an amenable number.

21521992 is a deficient number, since it is larger than the sum of its proper divisors (18831758).

21521992 is a wasteful number, since it uses less digits than its factorization.

21521992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2690255 (or 2690251 counting only the distinct ones).

The product of its digits is 3240, while the sum is 31.

The square root of 21521992 is about 4639.1800999746. The cubic root of 21521992 is about 278.1596653673.

The spelling of 21521992 in words is "twenty-one million, five hundred twenty-one thousand, nine hundred ninety-two".