1291642640 has 40 divisors (see below), whose sum is σ = 3008908608. Its totient is φ = 515652480.

The previous prime is 1291642637. The next prime is 1291642747. The reversal of 1291642640 is 462461921.

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

It is a self number, because there is not a number n which added to its sum of digits gives 1291642640.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26405 + ... + 57275.

Almost surely, 2^1291642640 is an apocalyptic number.

1291642640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1291642640 is an abundant number, since it is smaller than the sum of its proper divisors (1717265968).

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

1291642640 is a wasteful number, since it uses less digits than its factorization.

1291642640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31407 (or 31401 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 35.

The square root of 1291642640 is about 35939.4301568625. The cubic root of 1291642640 is about 1089.0490935247.

The spelling of 1291642640 in words is "one billion, two hundred ninety-one million, six hundred forty-two thousand, six hundred forty".