1247993721 has 24 divisors (see below), whose sum is σ = 1943168136. Its totient is φ = 767266560.

The previous prime is 1247993699. The next prime is 1247993723. The reversal of 1247993721 is 1273997421.

It can be written as a sum of positive squares in 4 ways, for example, as 98783721 + 1149210000 = 9939^2 + 33900^2 .

It is not a de Polignac number, because 1247993721 - 2¹⁵ = 1247960953 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1247993723) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 135111 + ... + 144051.

It is an arithmetic number, because the mean of its divisors is an integer number (80965339).

Almost surely, 2^1247993721 is an apocalyptic number.

It is an amenable number.

1247993721 is a deficient number, since it is larger than the sum of its proper divisors (695174415).

1247993721 is a wasteful number, since it uses less digits than its factorization.

1247993721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10153 (or 10150 counting only the distinct ones).

The product of its digits is 190512, while the sum is 45.

The square root of 1247993721 is about 35326.9545956059. The cubic root of 1247993721 is about 1076.6407167952.

The spelling of 1247993721 in words is "one billion, two hundred forty-seven million, nine hundred ninety-three thousand, seven hundred twenty-one".