399502594728721 has 27 divisors (see below), whose sum is σ = 449582973517083. Its totient is φ = 354729638598720.

The previous prime is 399502594728691. The next prime is 399502594728739. The reversal of 399502594728721 is 127827495205993.

The square root of 399502594728721 is 19987561.

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

It can be written as a sum of positive squares in only one way, i.e., 210931035606225 + 188571559122496 = 14523465^2 + 13732136^2 .

It is not a de Polignac number, because 399502594728721 - 2¹³ = 399502594720529 is a prime.

It is a super-2 number, since 2×399502594728721² (a number of 30 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399502594728781) 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, 9454095225 + ... + 9454137481.

Almost surely, 2^{399502594728721} is an apocalyptic number.

399502594728721 is the 19987561-st square number.

399502594728721 is the 9993781-st centered octagonal number.

It is an amenable number.

399502594728721 is a deficient number, since it is larger than the sum of its proper divisors (50080378788362).

399502594728721 is an frugal number, since it uses more digits than its factorization.

399502594728721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84622 (or 42311 counting only the distinct ones).

The product of its (nonzero) digits is 685843200, while the sum is 73.

The spelling of 399502594728721 in words is "three hundred ninety-nine trillion, five hundred two billion, five hundred ninety-four million, seven hundred twenty-eight thousand, seven hundred twenty-one".