21213880 has 64 divisors (see below), whose sum is σ = 50918400. Its totient is φ = 7931520.

The previous prime is 21213859. The next prime is 21213893. The reversal of 21213880 is 8831212.

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, 78145 + ... + 78415.

It is an arithmetic number, because the mean of its divisors is an integer number (795600).

Almost surely, 2^21213880 is an apocalyptic number.

21213880 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 21213880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25459200).

21213880 is an abundant number, since it is smaller than the sum of its proper divisors (29704520).

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

21213880 is a wasteful number, since it uses less digits than its factorization.

21213880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404 (or 400 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 21213880 is about 4605.8527983426. The cubic root of 21213880 is about 276.8258885762.

The spelling of 21213880 in words is "twenty-one million, two hundred thirteen thousand, eight hundred eighty".