21918690 has 48 divisors (see below), whose sum is σ = 57283200. Its totient is φ = 5814816.

The previous prime is 21918679. The next prime is 21918697. The reversal of 21918690 is 9681912.

It is a super-2 number, since 2×21918690² = 960857942632200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21918697) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21001 + ... + 22019.

It is an arithmetic number, because the mean of its divisors is an integer number (1193400).

Almost surely, 2^21918690 is an apocalyptic number.

21918690 is an abundant number, since it is smaller than the sum of its proper divisors (35364510).

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

21918690 is a wasteful number, since it uses less digits than its factorization.

21918690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1271 (or 1268 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21918690 is about 4681.7400611311. The cubic root of 21918690 is about 279.8583041563.

The spelling of 21918690 in words is "twenty-one million, nine hundred eighteen thousand, six hundred ninety".