398918991 has 8 divisors (see below), whose sum is σ = 563179824. Its totient is φ = 250302080.

The previous prime is 398918987. The next prime is 398919007. The reversal of 398918991 is 199819893.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 398918991 - 2² = 398918987 is a prime.

It is a super-2 number, since 2×398918991² = 318272722760916162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (398918981) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3910920 + ... + 3911021.

It is an arithmetic number, because the mean of its divisors is an integer number (70397478).

Almost surely, 2^398918991 is an apocalyptic number.

398918991 is a deficient number, since it is larger than the sum of its proper divisors (164260833).

398918991 is a wasteful number, since it uses less digits than its factorization.

398918991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7821961.

The product of its digits is 1259712, while the sum is 57.

The square root of 398918991 is about 19972.9564912158. The cubic root of 398918991 is about 736.1419556989.

The spelling of 398918991 in words is "three hundred ninety-eight million, nine hundred eighteen thousand, nine hundred ninety-one".