21768400 has 30 divisors (see below), whose sum is σ = 52299542. Its totient is φ = 8707200.

The previous prime is 21768391. The next prime is 21768407. The reversal of 21768400 is 486712.

It can be written as a sum of positive squares in 3 ways, for example, as 4562496 + 17205904 = 2136^2 + 4148^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21768407) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 26811 + ... + 27610.

Almost surely, 2^21768400 is an apocalyptic number.

21768400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21768400 is an abundant number, since it is smaller than the sum of its proper divisors (30531142).

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

21768400 is a wasteful number, since it uses less digits than its factorization.

21768400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54439 (or 54428 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 21768400 is about 4665.6617965729. The cubic root of 21768400 is about 279.2172013168.

The spelling of 21768400 in words is "twenty-one million, seven hundred sixty-eight thousand, four hundred".