21210718321 has 27 divisors (see below), whose sum is σ = 24435420321. Its totient is φ = 18399448704.

The previous prime is 21210718301. The next prime is 21210718387. The reversal of 21210718321 is 12381701212.

The square root of 21210718321 is 145639.

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 191517921 + 21019200400 = 13839^2 + 144980^2 .

It is not a de Polignac number, because 21210718321 - 2⁹ = 21210717809 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21210718321.

It is not an unprimeable number, because it can be changed into a prime (21210718301) 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, 32185890 + ... + 32186548.

Almost surely, 2^21210718321 is an apocalyptic number.

21210718321 is the 145639-th square number.

21210718321 is the 72820-th centered octagonal number.

It is an amenable number.

21210718321 is a deficient number, since it is larger than the sum of its proper divisors (3224702000).

21210718321 is an frugal number, since it uses more digits than its factorization.

21210718321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1378 (or 689 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 28.

The spelling of 21210718321 in words is "twenty-one billion, two hundred ten million, seven hundred eighteen thousand, three hundred twenty-one".