21616556 has 24 divisors (see below), whose sum is σ = 41023584. Its totient is φ = 9907200.

The previous prime is 21616549. The next prime is 21616559. The reversal of 21616556 is 65561612.

It is a super-2 number, since 2×21616556² = 934550986602272, which contains 22 as substring.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21616559) 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, 6476 + ... + 9228.

It is an arithmetic number, because the mean of its divisors is an integer number (1709316).

Almost surely, 2^21616556 is an apocalyptic number.

21616556 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21616556 is a deficient number, since it is larger than the sum of its proper divisors (19407028).

21616556 is a wasteful number, since it uses less digits than its factorization.

21616556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2921 (or 2919 counting only the distinct ones).

The product of its digits is 10800, while the sum is 32.

The square root of 21616556 is about 4649.3608162843. The cubic root of 21616556 is about 278.5664656828.

The spelling of 21616556 in words is "twenty-one million, six hundred sixteen thousand, five hundred fifty-six".