640987 has 12 divisors (see below), whose sum is σ = 714960. Its totient is φ = 572880.

The previous prime is 640973. The next prime is 640993. The reversal of 640987 is 789046.

It is not a de Polignac number, because 640987 - 2⁷ = 640859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 20662 + ... + 20692.

It is an arithmetic number, because the mean of its divisors is an integer number (59580).

2⁶⁴⁰⁹⁸⁷ is an apocalyptic number.

640987 is a deficient number, since it is larger than the sum of its proper divisors (73973).

640987 is a wasteful number, since it uses less digits than its factorization.

640987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114 (or 83 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 640987 is about 800.6166373490. The cubic root of 640987 is about 86.2216654108.

The spelling of 640987 in words is "six hundred forty thousand, nine hundred eighty-seven".