21053700 has 108 divisors (see below), whose sum is σ = 66857700. Its totient is φ = 5541120.

The previous prime is 21053699. The next prime is 21053707. The reversal of 21053700 is 735012.

It can be written as a sum of positive squares in 6 ways, for example, as 4260096 + 16793604 = 2064^2 + 4098^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21053707) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 134022 + ... + 134178.

Almost surely, 2^21053700 is an apocalyptic number.

21053700 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 21053700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33428850).

21053700 is an abundant number, since it is smaller than the sum of its proper divisors (45804000).

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

21053700 is a wasteful number, since it uses less digits than its factorization.

21053700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 326 (or 316 counting only the distinct ones).

The product of its (nonzero) digits is 210, while the sum is 18.

The square root of 21053700 is about 4588.4311044190. The cubic root of 21053700 is about 276.1273829136.

Adding to 21053700 its reverse (735012), we get a palindrome (21788712).

The spelling of 21053700 in words is "twenty-one million, fifty-three thousand, seven hundred".