21531144400 has 30 divisors (see below), whose sum is σ = 51728575382. Its totient is φ = 8612457600.

The previous prime is 21531144389. The next prime is 21531144421. The reversal of 21531144400 is 444113512.

It can be written as a sum of positive squares in 3 ways, for example, as 6346990224 + 15184154176 = 79668^2 + 123224^2 .

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 26913531 + ... + 26914330.

Almost surely, 2^21531144400 is an apocalyptic number.

21531144400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21531144400 is an abundant number, since it is smaller than the sum of its proper divisors (30197430982).

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

21531144400 is a wasteful number, since it uses less digits than its factorization.

21531144400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53827879 (or 53827868 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

Adding to 21531144400 its reverse (444113512), we get a palindrome (21975257912).

The spelling of 21531144400 in words is "twenty-one billion, five hundred thirty-one million, one hundred forty-four thousand, four hundred".