21561944 has 32 divisors (see below), whose sum is σ = 41448000. Its totient is φ = 10513152.

The previous prime is 21561931. The next prime is 21561949. The reversal of 21561944 is 44916512.

It is a self number, because there is not a number n which added to its sum of digits gives 21561944.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561949) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 68732 + ... + 69044.

It is an arithmetic number, because the mean of its divisors is an integer number (1295250).

Almost surely, 2^21561944 is an apocalyptic number.

It is an amenable number.

21561944 is a deficient number, since it is larger than the sum of its proper divisors (19886056).

21561944 is a wasteful number, since it uses less digits than its factorization.

21561944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 507 (or 503 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 21561944 is about 4643.4840367982. The cubic root of 21561944 is about 278.3316780313.

The spelling of 21561944 in words is "twenty-one million, five hundred sixty-one thousand, nine hundred forty-four".