21556799 has 12 divisors (see below), whose sum is σ = 24984888. Its totient is φ = 18441600.

The previous prime is 21556783. The next prime is 21556841. The reversal of 21556799 is 99765512.

It is a happy number.

It is not a de Polignac number, because 21556799 - 2⁴ = 21556783 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21556709) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 212 + ... + 6569.

It is an arithmetic number, because the mean of its divisors is an integer number (2082074).

Almost surely, 2^21556799 is an apocalyptic number.

21556799 is a deficient number, since it is larger than the sum of its proper divisors (3428089).

21556799 is a wasteful number, since it uses less digits than its factorization.

21556799 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6826 (or 6809 counting only the distinct ones).

The product of its digits is 170100, while the sum is 44.

The square root of 21556799 is about 4642.9300016261. The cubic root of 21556799 is about 278.3095382465.

The spelling of 21556799 in words is "twenty-one million, five hundred fifty-six thousand, seven hundred ninety-nine".