21722790 has 16 divisors (see below), whose sum is σ = 52134768. Its totient is φ = 5792736.

The previous prime is 21722759. The next prime is 21722791. The reversal of 21722790 is 9722712.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 724093 = 21722790 / (2 + 1 + 7 + 2 + 2 + 7 + 9 + 0).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21722791) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 362017 + ... + 362076.

It is an arithmetic number, because the mean of its divisors is an integer number (3258423).

Almost surely, 2^21722790 is an apocalyptic number.

21722790 is an abundant number, since it is smaller than the sum of its proper divisors (30411978).

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

21722790 is a wasteful number, since it uses less digits than its factorization.

21722790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724103.

The product of its (nonzero) digits is 3528, while the sum is 30.

The square root of 21722790 is about 4660.7713953808. The cubic root of 21722790 is about 279.0220560408.

The spelling of 21722790 in words is "twenty-one million, seven hundred twenty-two thousand, seven hundred ninety".