640621907 has 4 divisors (see below), whose sum is σ = 650183496. Its totient is φ = 631060320.

The previous prime is 640621903. The next prime is 640621951. The reversal of 640621907 is 709126046.

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

It is a cyclic number.

It is not a de Polignac number, because 640621907 - 2² = 640621903 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640621901) 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, 4780694 + ... + 4780827.

It is an arithmetic number, because the mean of its divisors is an integer number (162545874).

Almost surely, 2^640621907 is an apocalyptic number.

640621907 is a gapful number since it is divisible by the number (67) formed by its first and last digit.

640621907 is a deficient number, since it is larger than the sum of its proper divisors (9561589).

640621907 is an equidigital number, since it uses as much as digits as its factorization.

640621907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9561588.

The product of its (nonzero) digits is 18144, while the sum is 35.

The square root of 640621907 is about 25310.5098131191. The cubic root of 640621907 is about 862.0529227327.

The spelling of 640621907 in words is "six hundred forty million, six hundred twenty-one thousand, nine hundred seven".