399869721 has 12 divisors (see below), whose sum is σ = 579678372. Its totient is φ = 265615776.

The previous prime is 399869677. The next prime is 399869741. The reversal of 399869721 is 127968993.

It can be written as a sum of positive squares in 2 ways, for example, as 64979721 + 334890000 = 8061^2 + 18300^2 .

It is not a de Polignac number, because 399869721 - 2⁹ = 399869209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (399869741) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 77706 + ... + 82691.

It is an arithmetic number, because the mean of its divisors is an integer number (48306531).

Almost surely, 2^399869721 is an apocalyptic number.

It is an amenable number.

399869721 is a deficient number, since it is larger than the sum of its proper divisors (179808651).

399869721 is a wasteful number, since it uses less digits than its factorization.

399869721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160680 (or 160677 counting only the distinct ones).

The product of its digits is 1469664, while the sum is 54.

The square root of 399869721 is about 19996.7427597597. The cubic root of 399869721 is about 736.7262990522.

The spelling of 399869721 in words is "three hundred ninety-nine million, eight hundred sixty-nine thousand, seven hundred twenty-one".