21409980 has 48 divisors (see below), whose sum is σ = 60558624. Its totient is φ = 5651200.

The previous prime is 21409931. The next prime is 21409991. The reversal of 21409980 is 8990412.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4294 + ... + 7826.

It is an arithmetic number, because the mean of its divisors is an integer number (1261638).

Almost surely, 2^21409980 is an apocalyptic number.

21409980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21409980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30279312).

21409980 is an abundant number, since it is smaller than the sum of its proper divisors (39148644).

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

21409980 is a wasteful number, since it uses less digits than its factorization.

21409980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3646 (or 3644 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 21409980 is about 4627.0919593196. The cubic root of 21409980 is about 277.6762616898.

The spelling of 21409980 in words is "twenty-one million, four hundred nine thousand, nine hundred eighty".