21042520400 has 240 divisors, whose sum is σ = 56958854400. Its totient is φ = 7404748800.

The previous prime is 21042520397. The next prime is 21042520403. The reversal of 21042520400 is 402524012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21042520397) and next prime (21042520403).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042520403) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 20059076 + ... + 20060124.

It is an arithmetic number, because the mean of its divisors is an integer number (237328560).

Almost surely, 2^21042520400 is an apocalyptic number.

21042520400 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 21042520400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28479427200).

21042520400 is an abundant number, since it is smaller than the sum of its proper divisors (35916334000).

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

21042520400 is a wasteful number, since it uses less digits than its factorization.

21042520400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1222 (or 1211 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The spelling of 21042520400 in words is "twenty-one billion, forty-two million, five hundred twenty thousand, four hundred".