21320000 has 140 divisors (see below), whose sum is σ = 58321956. Its totient is φ = 7680000.

The previous prime is 21319997. The next prime is 21320021. The reversal of 21320000 is 2312.

It can be written as a sum of positive squares in 10 ways, for example, as 21307456 + 12544 = 4616^2 + 112^2 .

It is a Harshad number since it is a multiple of its sum of digits (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21320000.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 519980 + ... + 520020.

Almost surely, 2^21320000 is an apocalyptic number.

21320000 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 21320000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29160978).

21320000 is an abundant number, since it is smaller than the sum of its proper divisors (37001956).

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

21320000 is an equidigital number, since it uses as much as digits as its factorization.

21320000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86 (or 61 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 8.

The square root of 21320000 is about 4617.3585522461. The cubic root of 21320000 is about 277.2867175924.

Adding to 21320000 its reverse (2312), we get a palindrome (21322312).

The spelling of 21320000 in words is "twenty-one million, three hundred twenty thousand".