1640865813 has 4 divisors (see below), whose sum is σ = 2187821088. Its totient is φ = 1093910540.

The previous prime is 1640865803. The next prime is 1640865827. The reversal of 1640865813 is 3185680461.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1640865813 - 2¹⁴ = 1640849429 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1640865803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 273477633 + ... + 273477638.

It is an arithmetic number, because the mean of its divisors is an integer number (546955272).

Almost surely, 2^1640865813 is an apocalyptic number.

It is an amenable number.

1640865813 is a deficient number, since it is larger than the sum of its proper divisors (546955275).

1640865813 is an equidigital number, since it uses as much as digits as its factorization.

1640865813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546955274.

The product of its (nonzero) digits is 138240, while the sum is 42.

The square root of 1640865813 is about 40507.6019161836. The cubic root of 1640865813 is about 1179.4811980104.

The spelling of 1640865813 in words is "one billion, six hundred forty million, eight hundred sixty-five thousand, eight hundred thirteen".