391620987 has 28 divisors (see below), whose sum is σ = 603073680. Its totient is φ = 254006928.

The previous prime is 391620979. The next prime is 391620997. The reversal of 391620987 is 789026193.

It is not a de Polignac number, because 391620987 - 2³ = 391620979 is a prime.

It is not an unprimeable number, because it can be changed into a prime (391620907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 19714 + ... + 34232.

Almost surely, 2^391620987 is an apocalyptic number.

391620987 is a gapful number since it is divisible by the number (37) formed by its first and last digit.

391620987 is a deficient number, since it is larger than the sum of its proper divisors (211452693).

391620987 is an equidigital number, since it uses as much as digits as its factorization.

391620987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14574 (or 14559 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 45.

The square root of 391620987 is about 19789.4160348404. The cubic root of 391620987 is about 731.6251944422.

The spelling of 391620987 in words is "three hundred ninety-one million, six hundred twenty thousand, nine hundred eighty-seven".