391638240 has 288 divisors, whose sum is σ = 1585059840. Its totient is φ = 89455104.

The previous prime is 391638193. The next prime is 391638251. The reversal of 391638240 is 42836193.

It is a tau number, because it is divible by the number of its divisors (288).

It is a super-2 number, since 2×391638240² = 306761022060595200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 391638195 and 391638204.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 271441 + ... + 272879.

It is an arithmetic number, because the mean of its divisors is an integer number (5503680).

Almost surely, 2^391638240 is an apocalyptic number.

391638240 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 391638240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (792529920).

391638240 is an abundant number, since it is smaller than the sum of its proper divisors (1193421600).

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

391638240 is a wasteful number, since it uses less digits than its factorization.

391638240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1476 (or 1456 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 391638240 is about 19789.8519448732. The cubic root of 391638240 is about 731.6359382859.

The spelling of 391638240 in words is "three hundred ninety-one million, six hundred thirty-eight thousand, two hundred forty".