640981491 has 8 divisors (see below), whose sum is σ = 854810880. Its totient is φ = 427236552.

The previous prime is 640981433. The next prime is 640981493. The reversal of 640981491 is 194189046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 640981491 - 2¹⁴ = 640965107 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640981493) 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, 535 + ... + 35808.

It is an arithmetic number, because the mean of its divisors is an integer number (106851360).

Almost surely, 2^640981491 is an apocalyptic number.

640981491 is a deficient number, since it is larger than the sum of its proper divisors (213829389).

640981491 is a wasteful number, since it uses less digits than its factorization.

640981491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42225.

The product of its (nonzero) digits is 62208, while the sum is 42.

The square root of 640981491 is about 25317.6122689325. The cubic root of 640981491 is about 862.2141839774.

The spelling of 640981491 in words is "six hundred forty million, nine hundred eighty-one thousand, four hundred ninety-one".