391919890 has 16 divisors (see below), whose sum is σ = 717413760. Its totient is φ = 154110640.

The previous prime is 391919863. The next prime is 391919893. The reversal of 391919890 is 98919193.

It is a super-2 number, since 2×391919890² = 307202400355224200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (391919893) 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, 331546 + ... + 332725.

It is an arithmetic number, because the mean of its divisors is an integer number (44838360).

Almost surely, 2^391919890 is an apocalyptic number.

391919890 is a deficient number, since it is larger than the sum of its proper divisors (325493870).

391919890 is a wasteful number, since it uses less digits than its factorization.

391919890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 664337.

The product of its (nonzero) digits is 157464, while the sum is 49.

The square root of 391919890 is about 19796.9666868437. The cubic root of 391919890 is about 731.8112836794.

The spelling of 391919890 in words is "three hundred ninety-one million, nine hundred nineteen thousand, eight hundred ninety".