640669801 has 4 divisors (see below), whose sum is σ = 642192004. Its totient is φ = 639147600.

The previous prime is 640669789. The next prime is 640669811. The reversal of 640669801 is 108966046.

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

It can be written as a sum of positive squares in 2 ways, for example, as 145829776 + 494840025 = 12076^2 + 22245^2 .

It is a cyclic number.

It is not a de Polignac number, because 640669801 - 2¹⁵ = 640637033 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640669811) 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, 760470 + ... + 761311.

It is an arithmetic number, because the mean of its divisors is an integer number (160548001).

Almost surely, 2^640669801 is an apocalyptic number.

It is an amenable number.

640669801 is a deficient number, since it is larger than the sum of its proper divisors (1522203).

640669801 is a wasteful number, since it uses less digits than its factorization.

640669801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1522202.

The product of its (nonzero) digits is 62208, while the sum is 40.

The square root of 640669801 is about 25311.4559241463. The cubic root of 640669801 is about 862.0744050524.

The spelling of 640669801 in words is "six hundred forty million, six hundred sixty-nine thousand, eight hundred one".