21215972966400 has 405 divisors, whose sum is σ = 76029702722701. Its totient is φ = 5655234478080.

The previous prime is 21215972966327. The next prime is 21215972966431. The reversal of 21215972966400 is 466927951212.

It is a happy number.

The square root of 21215972966400 is 4606080.

It is a perfect power (a square), and thus also a powerful number.

21215972966400 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 597 + 2 + 9 + 6 + 6 + 40 + 0 = 666.

It can be written as a sum of positive squares in only one way, i.e., 7637750267904 + 13578222698496 = 2763648^2 + 3684864^2 .

It is a super-2 number, since 2×21215972966400² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 8843672401 + ... + 8843674799.

Almost surely, 2^{21215972966400} is an apocalyptic number.

21215972966400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21215972966400 is the 4606080-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21215972966400

21215972966400 is an abundant number, since it is smaller than the sum of its proper divisors (54813729756301).

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

21215972966400 is an frugal number, since it uses more digits than its factorization.

21215972966400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4842 (or 2409 counting only the distinct ones).

The product of its (nonzero) digits is 3265920, while the sum is 54.

The spelling of 21215972966400 in words is "twenty-one trillion, two hundred fifteen billion, nine hundred seventy-two million, nine hundred sixty-six thousand, four hundred".