1391639440 has 40 divisors (see below), whose sum is σ = 3237167808. Its totient is φ = 556379520.

The previous prime is 1391639423. The next prime is 1391639441. The reversal of 1391639440 is 449361931.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 1391639393 and 1391639402.

It is not an unprimeable number, because it can be changed into a prime (1391639441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 253525 + ... + 258955.

Almost surely, 2^1391639440 is an apocalyptic number.

1391639440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1391639440 is an abundant number, since it is smaller than the sum of its proper divisors (1845528368).

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

1391639440 is a wasteful number, since it uses less digits than its factorization.

1391639440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8647 (or 8641 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 40.

The square root of 1391639440 is about 37304.6838882197. The cubic root of 1391639440 is about 1116.4576216192.

The spelling of 1391639440 in words is "one billion, three hundred ninety-one million, six hundred thirty-nine thousand, four hundred forty".