21566402 has 16 divisors (see below), whose sum is σ = 38005632. Its totient is φ = 9048720.

The previous prime is 21566393. The next prime is 21566407. The reversal of 21566402 is 20466512.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is not an unprimeable number, because it can be changed into a prime (21566407) 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, 37418 + ... + 37989.

It is an arithmetic number, because the mean of its divisors is an integer number (2375352).

Almost surely, 2^21566402 is an apocalyptic number.

21566402 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21566402 is a deficient number, since it is larger than the sum of its proper divisors (16439230).

21566402 is a wasteful number, since it uses less digits than its factorization.

21566402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75433.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21566402 is about 4643.9640394818. The cubic root of 21566402 is about 278.3508586939.

It can be divided in two parts, 2156 and 6402, that added together give a palindrome (8558).

The spelling of 21566402 in words is "twenty-one million, five hundred sixty-six thousand, four hundred two".