21722780 has 12 divisors (see below), whose sum is σ = 45617880. Its totient is φ = 8689104.

The previous prime is 21722759. The next prime is 21722791. The reversal of 21722780 is 8722712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 543050 + ... + 543089.

It is an arithmetic number, because the mean of its divisors is an integer number (3801490).

Almost surely, 2^21722780 is an apocalyptic number.

21722780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21722780 is an abundant number, since it is smaller than the sum of its proper divisors (23895100).

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

21722780 is a wasteful number, since it uses less digits than its factorization.

21722780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1086148 (or 1086146 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 29.

The square root of 21722780 is about 4660.7703225969. The cubic root of 21722780 is about 279.0220132252.

The spelling of 21722780 in words is "twenty-one million, seven hundred twenty-two thousand, seven hundred eighty".