21722820 has 48 divisors (see below), whose sum is σ = 69514368. Its totient is φ = 4965120.

The previous prime is 21722801. The next prime is 21722837. The reversal of 21722820 is 2822712.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25441 + ... + 26280.

It is an arithmetic number, because the mean of its divisors is an integer number (1448216).

Almost surely, 2^21722820 is an apocalyptic number.

21722820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21722820 is an abundant number, since it is smaller than the sum of its proper divisors (47791548).

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

21722820 is a wasteful number, since it uses less digits than its factorization.

21722820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51740 (or 51738 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21722820 is about 4660.7746137311. The cubic root of 21722820 is about 279.0221844874.

The spelling of 21722820 in words is "twenty-one million, seven hundred twenty-two thousand, eight hundred twenty".