21821490 has 48 divisors (see below), whose sum is σ = 58278168. Its totient is φ = 5660928.

The previous prime is 21821479. The next prime is 21821507. The reversal of 21821490 is 9412812.

It can be written as a sum of positive squares in 4 ways, for example, as 19686969 + 2134521 = 4437^2 + 1461^2 .

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, 54 + ... + 6606.

Almost surely, 2^21821490 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21821490, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29139084).

21821490 is an abundant number, since it is smaller than the sum of its proper divisors (36456678).

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

21821490 is a wasteful number, since it uses less digits than its factorization.

21821490 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6603 (or 6600 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 21821490 is about 4671.3477712540. The cubic root of 21821490 is about 279.4440072466. Note that the first 3 decimals are identical.

The spelling of 21821490 in words is "twenty-one million, eight hundred twenty-one thousand, four hundred ninety".