399346899721 has 81 divisors (see below), whose sum is σ = 530707018023. Its totient is φ = 299387420640.

The previous prime is 399346899703. The next prime is 399346899769. The reversal of 399346899721 is 127998643993.

The square root of 399346899721 is 631939.

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., 209407827321 + 189939072400 = 457611^2 + 435820^2 .

It is not a de Polignac number, because 399346899721 - 2⁷ = 399346899593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (399346899221) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 1411119646 + ... + 1411119928.

Almost surely, 2^399346899721 is an apocalyptic number.

399346899721 is the 631939-th square number.

399346899721 is the 315970-th centered octagonal number.

It is an amenable number.

399346899721 is a deficient number, since it is larger than the sum of its proper divisors (131360118302).

399346899721 is an equidigital number, since it uses as much as digits as its factorization.

399346899721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 660 (or 330 counting only the distinct ones).

The product of its digits is 158723712, while the sum is 70.

The spelling of 399346899721 in words is "three hundred ninety-nine billion, three hundred forty-six million, eight hundred ninety-nine thousand, seven hundred twenty-one".