640020646 has 4 divisors (see below), whose sum is σ = 960030972. Its totient is φ = 320010322.

The previous prime is 640020611. The next prime is 640020659. The reversal of 640020646 is 646020046.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160005160 + ... + 160005163.

It is an arithmetic number, because the mean of its divisors is an integer number (240007743).

Almost surely, 2^640020646 is an apocalyptic number.

640020646 is a deficient number, since it is larger than the sum of its proper divisors (320010326).

640020646 is a wasteful number, since it uses less digits than its factorization.

640020646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320010325.

The product of its (nonzero) digits is 6912, while the sum is 28.

The square root of 640020646 is about 25298.6293304598. The cubic root of 640020646 is about 861.7831426753.

The spelling of 640020646 in words is "six hundred forty million, twenty thousand, six hundred forty-six".