391400640 has 224 divisors, whose sum is σ = 1399032000. Its totient is φ = 102998016.

The previous prime is 391400599. The next prime is 391400641. The reversal of 391400640 is 46004193.

391400640 is a `hidden beast` number, since 3 + 9 + 14 + 0 + 0 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (391400641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 768706 + ... + 769214.

Almost surely, 2^391400640 is an apocalyptic number.

391400640 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 391400640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (699516000).

391400640 is an abundant number, since it is smaller than the sum of its proper divisors (1007631360).

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

391400640 is a wasteful number, since it uses less digits than its factorization.

391400640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 624 (or 608 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 391400640 is about 19783.8479573616. The cubic root of 391400640 is about 731.4879514896.

The spelling of 391400640 in words is "three hundred ninety-one million, four hundred thousand, six hundred forty".