640713021 has 8 divisors (see below), whose sum is σ = 919998240. Its totient is φ = 394284912.

The previous prime is 640713019. The next prime is 640713049. The reversal of 640713021 is 120317046.

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

It is not a de Polignac number, because 640713021 - 2¹ = 640713019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640712982 and 640713000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640713091) 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, 8214231 + ... + 8214308.

It is an arithmetic number, because the mean of its divisors is an integer number (114999780).

Almost surely, 2^640713021 is an apocalyptic number.

It is an amenable number.

640713021 is a deficient number, since it is larger than the sum of its proper divisors (279285219).

640713021 is a wasteful number, since it uses less digits than its factorization.

640713021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16428555.

The product of its (nonzero) digits is 1008, while the sum is 24.

The square root of 640713021 is about 25312.3096733585. The cubic root of 640713021 is about 862.0937899825.

The spelling of 640713021 in words is "six hundred forty million, seven hundred thirteen thousand, twenty-one".