391978755 has 72 divisors (see below), whose sum is σ = 796150368. Its totient is φ = 174763008.

The previous prime is 391978751. The next prime is 391978789. The reversal of 391978755 is 557879193.

It is not a de Polignac number, because 391978755 - 2² = 391978751 is a prime.

It is not an unprimeable number, because it can be changed into a prime (391978751) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 582099 + ... + 582771.

It is an arithmetic number, because the mean of its divisors is an integer number (11057644).

Almost surely, 2^391978755 is an apocalyptic number.

391978755 is a gapful number since it is divisible by the number (35) formed by its first and last digit.

391978755 is an abundant number, since it is smaller than the sum of its proper divisors (404171613).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

391978755 is a wasteful number, since it uses less digits than its factorization.

391978755 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 777 (or 731 counting only the distinct ones).

The product of its digits is 2381400, while the sum is 54.

The square root of 391978755 is about 19798.4533486836. The cubic root of 391978755 is about 731.8479203457.

The spelling of 391978755 in words is "three hundred ninety-one million, nine hundred seventy-eight thousand, seven hundred fifty-five".