640867069 has 4 divisors (see below), whose sum is σ = 647474044. Its totient is φ = 634260096.

The previous prime is 640867049. The next prime is 640867079. The reversal of 640867069 is 960768046.

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 85322169 + 555544900 = 9237^2 + 23570^2 .

It is a cyclic number.

It is not a de Polignac number, because 640867069 - 2⁹ = 640866557 is a prime.

It is a super-2 number, since 2×640867069² = 821421200257301522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640867049) 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, 3303342 + ... + 3303535.

It is an arithmetic number, because the mean of its divisors is an integer number (161868511).

Almost surely, 2^640867069 is an apocalyptic number.

It is an amenable number.

640867069 is a deficient number, since it is larger than the sum of its proper divisors (6606975).

640867069 is an equidigital number, since it uses as much as digits as its factorization.

640867069 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6606974.

The product of its (nonzero) digits is 435456, while the sum is 46.

The square root of 640867069 is about 25315.3524368119. The cubic root of 640867069 is about 862.1628761296.

The spelling of 640867069 in words is "six hundred forty million, eight hundred sixty-seven thousand, sixty-nine".