19757394721 has 9 divisors (see below), whose sum is σ = 19863238161. Its totient is φ = 19652114532.

The previous prime is 19757394719. The next prime is 19757394733. The reversal of 19757394721 is 12749375791.

It is a happy number.

The square root of 19757394721 is 140561.

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

It is not a de Polignac number, because 19757394721 - 2¹ = 19757394719 is a prime.

It is a super-2 number, since 2×19757394721² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19757394121) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 51585696 + ... + 51586078.

Almost surely, 2^19757394721 is an apocalyptic number.

19757394721 is the 140561-st square number.

19757394721 is the 70281-st centered octagonal number.

It is an amenable number.

19757394721 is a deficient number, since it is larger than the sum of its proper divisors (105843440).

19757394721 is an frugal number, since it uses more digits than its factorization.

19757394721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1500 (or 750 counting only the distinct ones).

The product of its digits is 3333960, while the sum is 55.

The spelling of 19757394721 in words is "nineteen billion, seven hundred fifty-seven million, three hundred ninety-four thousand, seven hundred twenty-one".