21790660 has 48 divisors (see below), whose sum is σ = 48254976. Its totient is φ = 8249472.

The previous prime is 21790633. The next prime is 21790673. The reversal of 21790660 is 6609712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 58234 + ... + 58606.

It is an arithmetic number, because the mean of its divisors is an integer number (1005312).

Almost surely, 2^21790660 is an apocalyptic number.

21790660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21790660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24127488).

21790660 is an abundant number, since it is smaller than the sum of its proper divisors (26464316).

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

21790660 is a wasteful number, since it uses less digits than its factorization.

21790660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 532 (or 530 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 31.

The square root of 21790660 is about 4668.0467007090. The cubic root of 21790660 is about 279.3123431665.

The spelling of 21790660 in words is "twenty-one million, seven hundred ninety thousand, six hundred sixty".