21820788 has 36 divisors (see below), whose sum is σ = 60173568. Its totient is φ = 6612240.

The previous prime is 21820781. The next prime is 21820793. The reversal of 21820788 is 88702812.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×21820788² = 952293577881888, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820781) 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, 27156 + ... + 27947.

It is an arithmetic number, because the mean of its divisors is an integer number (1671488).

Almost surely, 2^21820788 is an apocalyptic number.

It is an amenable number.

21820788 is an abundant number, since it is smaller than the sum of its proper divisors (38352780).

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

21820788 is a wasteful number, since it uses less digits than its factorization.

21820788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55124 (or 55119 counting only the distinct ones).

The product of its (nonzero) digits is 14336, while the sum is 36.

The square root of 21820788 is about 4671.2726317354. The cubic root of 21820788 is about 279.4410106319.

The spelling of 21820788 in words is "twenty-one million, eight hundred twenty thousand, seven hundred eighty-eight".