636121643 has 4 divisors (see below), whose sum is σ = 656641728. Its totient is φ = 615601560.

The previous prime is 636121639. The next prime is 636121663. The reversal of 636121643 is 346121636.

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 636121643 - 2² = 636121639 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (636121663) 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, 10259996 + ... + 10260057.

It is an arithmetic number, because the mean of its divisors is an integer number (164160432).

Almost surely, 2^636121643 is an apocalyptic number.

636121643 is a deficient number, since it is larger than the sum of its proper divisors (20520085).

636121643 is a wasteful number, since it uses less digits than its factorization.

636121643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20520084.

The product of its digits is 15552, while the sum is 32.

The square root of 636121643 is about 25221.4520398807. The cubic root of 636121643 is about 860.0295838931.

The spelling of 636121643 in words is "six hundred thirty-six million, one hundred twenty-one thousand, six hundred forty-three".