1640656819 has 4 divisors (see below), whose sum is σ = 1641028896. Its totient is φ = 1640284744.

The previous prime is 1640656811. The next prime is 1640656841. The reversal of 1640656819 is 9186560461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9186560461 = 13 ⋅706658497.

It is a cyclic number.

It is not a de Polignac number, because 1640656819 - 2³ = 1640656811 is a prime.

It is a super-2 number, since 2×1640656819² = 5383509595462397522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1640656811) 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, 179344 + ... + 188269.

It is an arithmetic number, because the mean of its divisors is an integer number (410257224).

Almost surely, 2^1640656819 is an apocalyptic number.

1640656819 is a deficient number, since it is larger than the sum of its proper divisors (372077).

1640656819 is an equidigital number, since it uses as much as digits as its factorization.

1640656819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372076.

The product of its (nonzero) digits is 311040, while the sum is 46.

The square root of 1640656819 is about 40505.0221454081. The cubic root of 1640656819 is about 1179.4311197818.

The spelling of 1640656819 in words is "one billion, six hundred forty million, six hundred fifty-six thousand, eight hundred nineteen".