21247943972 has 24 divisors (see below), whose sum is σ = 38225556600. Its totient is φ = 10326908160.

The previous prime is 21247943971. The next prime is 21247944001. The reversal of 21247943972 is 27934974212.

It can be written as a sum of positive squares in 4 ways, for example, as 8789812516 + 12458131456 = 93754^2 + 111616^2 .

It is a super-2 number, since 2×21247943972² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21247943972.

It is not an unprimeable number, because it can be changed into a prime (21247943971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 86822 + ... + 223682.

It is an arithmetic number, because the mean of its divisors is an integer number (1592731525).

Almost surely, 2^21247943972 is an apocalyptic number.

It is an amenable number.

21247943972 is a deficient number, since it is larger than the sum of its proper divisors (16977612628).

21247943972 is a wasteful number, since it uses less digits than its factorization.

21247943972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137951 (or 137949 counting only the distinct ones).

The product of its digits is 1524096, while the sum is 50.

The spelling of 21247943972 in words is "twenty-one billion, two hundred forty-seven million, nine hundred forty-three thousand, nine hundred seventy-two".