21021440400 has 360 divisors, whose sum is σ = 78106236000. Its totient is φ = 5219665920.

The previous prime is 21021440371. The next prime is 21021440413. The reversal of 21021440400 is 404412012.

21021440400 is a `hidden beast` number, since 2 + 10 + 214 + 40 + 400 = 666.

It is a tau number, because it is divible by the number of its divisors (360).

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

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 4032996 + ... + 4038204.

Almost surely, 2^21021440400 is an apocalyptic number.

21021440400 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 21021440400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39053118000).

21021440400 is an abundant number, since it is smaller than the sum of its proper divisors (57084795600).

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

21021440400 is a wasteful number, since it uses less digits than its factorization.

21021440400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5311 (or 5297 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

Adding to 21021440400 its reverse (404412012), we get a palindrome (21425852412).

The spelling of 21021440400 in words is "twenty-one billion, twenty-one million, four hundred forty thousand, four hundred".