391389731 has 4 divisors (see below), whose sum is σ = 400935864. Its totient is φ = 381843600.

The previous prime is 391389673. The next prime is 391389749. The reversal of 391389731 is 137983193.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 137983193 = 1733 ⋅79621.

It is a cyclic number.

It is not a de Polignac number, because 391389731 - 2¹⁸ = 391127587 is a prime.

It is a super-2 number, since 2×391389731² = 306371843064504722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391389331) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4773005 + ... + 4773086.

It is an arithmetic number, because the mean of its divisors is an integer number (100233966).

Almost surely, 2^391389731 is an apocalyptic number.

391389731 is a deficient number, since it is larger than the sum of its proper divisors (9546133).

391389731 is an equidigital number, since it uses as much as digits as its factorization.

391389731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9546132.

The product of its digits is 122472, while the sum is 44.

The square root of 391389731 is about 19783.5722507337. The cubic root of 391389731 is about 731.4811554897.

The spelling of 391389731 in words is "three hundred ninety-one million, three hundred eighty-nine thousand, seven hundred thirty-one".