21820280 has 32 divisors (see below), whose sum is σ = 50682240. Its totient is φ = 8446080.

The previous prime is 21820273. The next prime is 21820283. The reversal of 21820280 is 8202812.

It is a super-2 number, since 2×21820280² = 952249238556800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820283) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7559 + ... + 10038.

It is an arithmetic number, because the mean of its divisors is an integer number (1583820).

Almost surely, 2^21820280 is an apocalyptic number.

21820280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21820280 is an abundant number, since it is smaller than the sum of its proper divisors (28861960).

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

21820280 is a wasteful number, since it uses less digits than its factorization.

21820280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17639 (or 17635 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 23.

The square root of 21820280 is about 4671.2182565151. The cubic root of 21820280 is about 279.4388421013.

The spelling of 21820280 in words is "twenty-one million, eight hundred twenty thousand, two hundred eighty".