21768820 has 24 divisors (see below), whose sum is σ = 47190528. Its totient is φ = 8426400.

The previous prime is 21768811. The next prime is 21768847. The reversal of 21768820 is 2886712.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16936 + ... + 18175.

It is an arithmetic number, because the mean of its divisors is an integer number (1966272).

Almost surely, 2^21768820 is an apocalyptic number.

21768820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21768820 is an abundant number, since it is smaller than the sum of its proper divisors (25421708).

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

21768820 is a wasteful number, since it uses less digits than its factorization.

21768820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35151 (or 35149 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 34.

The square root of 21768820 is about 4665.7068060477. The cubic root of 21768820 is about 279.2189970462.

The spelling of 21768820 in words is "twenty-one million, seven hundred sixty-eight thousand, eight hundred twenty".