21315400 has 48 divisors (see below), whose sum is σ = 49901940. Its totient is φ = 8467200.

The previous prime is 21315391. The next prime is 21315421. The reversal of 21315400 is 451312.

It can be written as a sum of positive squares in 6 ways, for example, as 13351716 + 7963684 = 3654^2 + 2822^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 39130 + ... + 39670.

Almost surely, 2^21315400 is an apocalyptic number.

21315400 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 21315400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24950970).

21315400 is an abundant number, since it is smaller than the sum of its proper divisors (28586540).

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

21315400 is a wasteful number, since it uses less digits than its factorization.

21315400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 754 (or 745 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21315400 is about 4616.8604050805. The cubic root of 21315400 is about 277.2667737111.

Adding to 21315400 its reverse (451312), we get a palindrome (21766712).

The spelling of 21315400 in words is "twenty-one million, three hundred fifteen thousand, four hundred".