21180990 has 16 divisors (see below), whose sum is σ = 50834448. Its totient is φ = 5648256.

The previous prime is 21180949. The next prime is 21181001. The reversal of 21180990 is 9908112.

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: 706033 = 21180990 / (2 + 1 + 1 + 8 + 0 + 9 + 9 + 0).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 352987 + ... + 353046.

It is an arithmetic number, because the mean of its divisors is an integer number (3177153).

Almost surely, 2^21180990 is an apocalyptic number.

21180990 is an abundant number, since it is smaller than the sum of its proper divisors (29653458).

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

21180990 is a wasteful number, since it uses less digits than its factorization.

21180990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 706043.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 21180990 is about 4602.2809562216. The cubic root of 21180990 is about 276.6827509560.

The spelling of 21180990 in words is "twenty-one million, one hundred eighty thousand, nine hundred ninety".