1640669897 has 4 divisors (see below), whose sum is σ = 1642855296. Its totient is φ = 1638484500.

The previous prime is 1640669887. The next prime is 1640669903. The reversal of 1640669897 is 7989660461.

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, and also an emirpimes, since its reverse is a distinct semiprime: 7989660461 = 257 ⋅31088173.

It is a cyclic number.

It is not a de Polignac number, because 1640669897 - 2¹⁴ = 1640653513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1640669827) 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, 1091573 + ... + 1093074.

It is an arithmetic number, because the mean of its divisors is an integer number (410713824).

Almost surely, 2^1640669897 is an apocalyptic number.

It is an amenable number.

1640669897 is a deficient number, since it is larger than the sum of its proper divisors (2185399).

1640669897 is an equidigital number, since it uses as much as digits as its factorization.

1640669897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2185398.

The product of its (nonzero) digits is 3919104, while the sum is 56.

The square root of 1640669897 is about 40505.1835818578. The cubic root of 1640669897 is about 1179.4342535997.

The spelling of 1640669897 in words is "one billion, six hundred forty million, six hundred sixty-nine thousand, eight hundred ninety-seven".