391287961 has 9 divisors (see below), whose sum is σ = 396926229. Its totient is φ = 385729500.

The previous prime is 391287959. The next prime is 391287971. The reversal of 391287961 is 169782193.

It is a happy number.

The square root of 391287961 is 19781.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 391287961 - 2¹ = 391287959 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391287931) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2591236 + ... + 2591386.

Almost surely, 2^391287961 is an apocalyptic number.

391287961 is the 19781-st square number.

391287961 is the 9891-st centered octagonal number.

It is an amenable number.

391287961 is a deficient number, since it is larger than the sum of its proper divisors (5638268).

391287961 is an frugal number, since it uses more digits than its factorization.

391287961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 564 (or 282 counting only the distinct ones).

The product of its digits is 163296, while the sum is 46.

The cubic root of 391287961 is about 731.4177495591.

It can be divided in two parts, 39128 and 7961, that added together give a square (47089 = 217²).

The spelling of 391287961 in words is "three hundred ninety-one million, two hundred eighty-seven thousand, nine hundred sixty-one".