21053900 has 72 divisors (see below), whose sum is σ = 54996480. Its totient is φ = 6834240.

The previous prime is 21053897. The next prime is 21053909. The reversal of 21053900 is 935012.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is not an unprimeable number, because it can be changed into a prime (21053909) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12509 + ... + 14091.

It is an arithmetic number, because the mean of its divisors is an integer number (763840).

Almost surely, 2^21053900 is an apocalyptic number.

21053900 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 21053900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27498240).

21053900 is an abundant number, since it is smaller than the sum of its proper divisors (33942580).

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

21053900 is a wasteful number, since it uses less digits than its factorization.

21053900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1623 (or 1616 counting only the distinct ones).

The product of its (nonzero) digits is 270, while the sum is 20.

The square root of 21053900 is about 4588.4528983090. The cubic root of 21053900 is about 276.1282572698.

Adding to 21053900 its reverse (935012), we get a palindrome (21988912).

The spelling of 21053900 in words is "twenty-one million, fifty-three thousand, nine hundred".