21787290 has 48 divisors (see below), whose sum is σ = 64741248. Its totient is φ = 4979808.

The previous prime is 21787237. The next prime is 21787301. The reversal of 21787290 is 9278712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 16662 + ... + 17921.

It is an arithmetic number, because the mean of its divisors is an integer number (1348776).

Almost surely, 2^21787290 is an apocalyptic number.

21787290 is an abundant number, since it is smaller than the sum of its proper divisors (42953958).

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

21787290 is a wasteful number, since it uses less digits than its factorization.

21787290 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34603 (or 34600 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 21787290 is about 4667.6857220683. The cubic root of 21787290 is about 279.2979435548.

The spelling of 21787290 in words is "twenty-one million, seven hundred eighty-seven thousand, two hundred ninety".