398831557 has 2 divisors, whose sum is σ = 398831558. Its totient is φ = 398831556.

The previous prime is 398831551. The next prime is 398831581. The reversal of 398831557 is 755138893.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 358496356 + 40335201 = 18934^2 + 6351^2 .

It is an emirp because it is prime and its reverse (755138893) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-398831557 is a prime.

It is a super-2 number, since 2×398831557² = 318133221718088498, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 398831557.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (398831551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199415778 + 199415779.

It is an arithmetic number, because the mean of its divisors is an integer number (199415779).

Almost surely, 2^398831557 is an apocalyptic number.

It is an amenable number.

398831557 is a deficient number, since it is larger than the sum of its proper divisors (1).

398831557 is an equidigital number, since it uses as much as digits as its factorization.

398831557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 907200, while the sum is 49.

The square root of 398831557 is about 19970.7675616136. The cubic root of 398831557 is about 736.0881698926.

The spelling of 398831557 in words is "three hundred ninety-eight million, eight hundred thirty-one thousand, five hundred fifty-seven".