1640664391 has 4 divisors (see below), whose sum is σ = 1675572192. Its totient is φ = 1605756592.

The previous prime is 1640664353. The next prime is 1640664419. The reversal of 1640664391 is 1934660461.

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 1640664391 - 2¹⁵ = 1640631623 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1640644391) 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, 17453830 + ... + 17453923.

It is an arithmetic number, because the mean of its divisors is an integer number (418893048).

Almost surely, 2^1640664391 is an apocalyptic number.

1640664391 is a deficient number, since it is larger than the sum of its proper divisors (34907801).

1640664391 is an equidigital number, since it uses as much as digits as its factorization.

1640664391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34907800.

The product of its (nonzero) digits is 93312, while the sum is 40.

The square root of 1640664391 is about 40505.1156151911. The cubic root of 1640664391 is about 1179.4329342256.

The spelling of 1640664391 in words is "one billion, six hundred forty million, six hundred sixty-four thousand, three hundred ninety-one".