21561612 has 12 divisors (see below), whose sum is σ = 50310456. Its totient is φ = 7187200.

The previous prime is 21561607. The next prime is 21561629. The reversal of 21561612 is 21616512.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-2 number, since 2×21561612² = 929806224077088, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 898389 + ... + 898412.

It is an arithmetic number, because the mean of its divisors is an integer number (4192538).

Almost surely, 2^21561612 is an apocalyptic number.

It is an amenable number.

21561612 is an abundant number, since it is smaller than the sum of its proper divisors (28748844).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21561612 is a wasteful number, since it uses less digits than its factorization.

21561612 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1796808 (or 1796806 counting only the distinct ones).

The product of its digits is 720, while the sum is 24.

The square root of 21561612 is about 4643.4482876414. The cubic root of 21561612 is about 278.3302494868.

The spelling of 21561612 in words is "twenty-one million, five hundred sixty-one thousand, six hundred twelve".