21053820 has 48 divisors (see below), whose sum is σ = 62421408. Its totient is φ = 5283840.

The previous prime is 21053783. The next prime is 21053831. The reversal of 21053820 is 2835012.

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, 9301 + ... + 11340.

It is an arithmetic number, because the mean of its divisors is an integer number (1300446).

Almost surely, 2^21053820 is an apocalyptic number.

21053820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21053820 is an abundant number, since it is smaller than the sum of its proper divisors (41367588).

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

21053820 is a wasteful number, since it uses less digits than its factorization.

21053820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20670 (or 20668 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21053820 is about 4588.4441807654. Note that the first 3 decimals coincide. The cubic root of 21053820 is about 276.1279075280.

Adding to 21053820 its reverse (2835012), we get a palindrome (23888832).

The spelling of 21053820 in words is "twenty-one million, fifty-three thousand, eight hundred twenty".