21790840 has 16 divisors (see below), whose sum is σ = 49029480. Its totient is φ = 8716320.

The previous prime is 21790801. The next prime is 21790841. The reversal of 21790840 is 4809712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21790841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 272346 + ... + 272425.

Almost surely, 2^21790840 is an apocalyptic number.

21790840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21790840 is an abundant number, since it is smaller than the sum of its proper divisors (27238640).

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

21790840 is a wasteful number, since it uses less digits than its factorization.

21790840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 544782 (or 544778 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21790840 is about 4668.0659806819. The cubic root of 21790840 is about 279.3131122435.

The spelling of 21790840 in words is "twenty-one million, seven hundred ninety thousand, eight hundred forty".