640858837 has 4 divisors (see below), whose sum is σ = 647204076. Its totient is φ = 634513600.

The previous prime is 640858831. The next prime is 640858859. The reversal of 640858837 is 738858046.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 291692241 + 349166596 = 17079^2 + 18686^2 .

It is a cyclic number.

It is not a de Polignac number, because 640858837 - 2¹⁹ = 640334549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640858831) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3172468 + ... + 3172669.

It is an arithmetic number, because the mean of its divisors is an integer number (161801019).

Almost surely, 2^640858837 is an apocalyptic number.

It is an amenable number.

640858837 is a deficient number, since it is larger than the sum of its proper divisors (6345239).

640858837 is a wasteful number, since it uses less digits than its factorization.

640858837 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6345238.

The product of its (nonzero) digits is 1290240, while the sum is 49.

The square root of 640858837 is about 25315.1898472044. The cubic root of 640858837 is about 862.1591845918.

The spelling of 640858837 in words is "six hundred forty million, eight hundred fifty-eight thousand, eight hundred thirty-seven".