21221321400 has 72 divisors (see below), whose sum is σ = 71268277080. Its totient is φ = 5659018560.

The previous prime is 21221321377. The next prime is 21221321411. The reversal of 21221321400 is 412312212.

It is a happy number.

21221321400 is a `hidden beast` number, since 21 + 221 + 3 + 21 + 400 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a super-3 number, since 3×21221321400³ (a number of 32 digits) contains 333 as substring.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 5893012 + ... + 5896611.

Almost surely, 2^21221321400 is an apocalyptic number.

21221321400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221321400 is an abundant number, since it is smaller than the sum of its proper divisors (50046955680).

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

21221321400 is a wasteful number, since it uses less digits than its factorization.

21221321400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11789645 (or 11789633 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

Adding to 21221321400 its reverse (412312212), we get a palindrome (21633633612).

The spelling of 21221321400 in words is "twenty-one billion, two hundred twenty-one million, three hundred twenty-one thousand, four hundred".