1640008891 has 4 divisors (see below), whose sum is σ = 1640090232. Its totient is φ = 1639927552.

The previous prime is 1640008861. The next prime is 1640008913. The reversal of 1640008891 is 1988000461.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1640008891 - 2⁷ = 1640008763 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1640008891.

It is not an unprimeable number, because it can be changed into a prime (1640008801) 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, 14715 + ... + 59131.

It is an arithmetic number, because the mean of its divisors is an integer number (410022558).

Almost surely, 2^1640008891 is an apocalyptic number.

1640008891 is a deficient number, since it is larger than the sum of its proper divisors (81341).

1640008891 is an equidigital number, since it uses as much as digits as its factorization.

1640008891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81340.

The product of its (nonzero) digits is 13824, while the sum is 37.

The square root of 1640008891 is about 40497.0232362824. The cubic root of 1640008891 is about 1179.2758390720.

The spelling of 1640008891 in words is "one billion, six hundred forty million, eight thousand, eight hundred ninety-one".