1638661567 has 4 divisors (see below), whose sum is σ = 1642789576. Its totient is φ = 1634533560.

The previous prime is 1638661561. The next prime is 1638661571. The reversal of 1638661567 is 7651668361.

It is a happy number.

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 1638661567 - 2²⁷ = 1504443839 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 1638661567.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638661561) 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, 2063409 + ... + 2064202.

It is an arithmetic number, because the mean of its divisors is an integer number (410697394).

Almost surely, 2^1638661567 is an apocalyptic number.

1638661567 is a deficient number, since it is larger than the sum of its proper divisors (4128009).

1638661567 is an equidigital number, since it uses as much as digits as its factorization.

1638661567 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4128008.

The product of its digits is 1088640, while the sum is 49.

The square root of 1638661567 is about 40480.3849660549. The cubic root of 1638661567 is about 1178.9528119732.

The spelling of 1638661567 in words is "one billion, six hundred thirty-eight million, six hundred sixty-one thousand, five hundred sixty-seven".