21561402 has 32 divisors (see below), whose sum is σ = 44029440. Its totient is φ = 7038000.

The previous prime is 21561401. The next prime is 21561427. The reversal of 21561402 is 20416512.

It is not an unprimeable number, because it can be changed into a prime (21561401) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 85777 + ... + 86027.

It is an arithmetic number, because the mean of its divisors is an integer number (1375920).

Almost surely, 2^21561402 is an apocalyptic number.

21561402 is an abundant number, since it is smaller than the sum of its proper divisors (22468038).

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

21561402 is a wasteful number, since it uses less digits than its factorization.

21561402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 498.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21561402 is about 4643.4256750808. The cubic root of 21561402 is about 278.3293458817.

Adding to 21561402 its reverse (20416512), we get a palindrome (41977914).

The spelling of 21561402 in words is "twenty-one million, five hundred sixty-one thousand, four hundred two".