21721143537 has 12 divisors (see below), whose sum is σ = 31376304180. Its totient is φ = 14480153568.

The previous prime is 21721143523. The next prime is 21721143553. The reversal of 21721143537 is 73534112712.

21721143537 is a `hidden beast` number, since 2 + 1 + 7 + 2 + 114 + 3 + 537 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 10979686656 + 10741456881 = 104784^2 + 103641^2 .

It is not a de Polignac number, because 21721143537 - 2²⁶ = 21654034673 is a prime.

It is a super-4 number, since 4×21721143537⁴ (a number of 42 digits) contains 4444 as substring.

It is not an unprimeable number, because it can be changed into a prime (21721143737) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 310923 + ... + 374319.

It is an arithmetic number, because the mean of its divisors is an integer number (2614692015).

Almost surely, 2^21721143537 is an apocalyptic number.

It is an amenable number.

21721143537 is a deficient number, since it is larger than the sum of its proper divisors (9655160643).

21721143537 is a wasteful number, since it uses less digits than its factorization.

21721143537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101472 (or 101469 counting only the distinct ones).

The product of its digits is 35280, while the sum is 36.

The spelling of 21721143537 in words is "twenty-one billion, seven hundred twenty-one million, one hundred forty-three thousand, five hundred thirty-seven".