640981785 has 8 divisors (see below), whose sum is σ = 1025570880. Its totient is φ = 341856944.

The previous prime is 640981769. The next prime is 640981811. The reversal of 640981785 is 587189046.

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

It is a cyclic number.

It is not a de Polignac number, because 640981785 - 2⁴ = 640981769 is a prime.

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, 21366045 + ... + 21366074.

It is an arithmetic number, because the mean of its divisors is an integer number (128196360).

Almost surely, 2^640981785 is an apocalyptic number.

It is an amenable number.

640981785 is a deficient number, since it is larger than the sum of its proper divisors (384589095).

640981785 is a wasteful number, since it uses less digits than its factorization.

640981785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42732127.

The product of its (nonzero) digits is 483840, while the sum is 48.

The square root of 640981785 is about 25317.6180751665. The cubic root of 640981785 is about 862.2143158018.

The spelling of 640981785 in words is "six hundred forty million, nine hundred eighty-one thousand, seven hundred eighty-five".