640393637 has 8 divisors (see below), whose sum is σ = 706476120. Its totient is φ = 576714240.

The previous prime is 640393603. The next prime is 640393657. The reversal of 640393637 is 736393046.

It is a Cunningham number, because it is equal to 25306²+1.

It can be written as a sum of positive squares in 4 ways, for example, as 30846916 + 609546721 = 5554^2 + 24689^2 .

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 640393637 - 2¹⁴ = 640377253 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 640393594 and 640393603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640393657) 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, 600212 + ... + 601277.

It is an arithmetic number, because the mean of its divisors is an integer number (88309515).

Almost surely, 2^640393637 is an apocalyptic number.

It is an amenable number.

640393637 is a deficient number, since it is larger than the sum of its proper divisors (66082483).

640393637 is a wasteful number, since it uses less digits than its factorization.

640393637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1201543.

The product of its (nonzero) digits is 244944, while the sum is 41.

The square root of 640393637 is about 25306.0000197582. Note that the first 4 decimals coincide. The cubic root of 640393637 is about 861.9505200540.

It can be divided in two parts, 64039 and 3637, that added together give a palindrome (67676).

The spelling of 640393637 in words is "six hundred forty million, three hundred ninety-three thousand, six hundred thirty-seven".