21279399961600 has 297 divisors, whose sum is σ = 58000394694403. Its totient is φ = 7735011328000.

The previous prime is 21279399961579. The next prime is 21279399961609. The reversal of 21279399961600 is 616999397212.

It is a happy number.

The square root of 21279399961600 is 4612960.

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

It can be written as a sum of positive squares in 4 ways, for example, as 928185803776 + 20351214157824 = 963424^2 + 4511232^2 .

It is a Harshad number since it is a multiple of its sum of digits (64).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21279399961609) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 8118808290 + ... + 8118810910.

Almost surely, 2^{21279399961600} is an apocalyptic number.

21279399961600 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21279399961600 is the 4612960-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21279399961600

21279399961600 is an abundant number, since it is smaller than the sum of its proper divisors (36720994732803).

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

21279399961600 is an frugal number, since it uses more digits than its factorization.

21279399961600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5294 (or 2639 counting only the distinct ones).

The product of its (nonzero) digits is 19840464, while the sum is 64.

21279399961600 divided by its sum of digits (64) gives a square (332490624400 = 576620²).

The spelling of 21279399961600 in words is "twenty-one trillion, two hundred seventy-nine billion, three hundred ninety-nine million, nine hundred sixty-one thousand, six hundred".