643666253642 has 4 divisors (see below), whose sum is σ = 965499380466. Its totient is φ = 321833126820.

The previous prime is 643666253641. The next prime is 643666253683. The reversal of 643666253642 is 246352666346.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 246352666346 = 2 ⋅123176333173.

It can be written as a sum of positive squares in only one way, i.e., 639438523201 + 4227730441 = 799649^2 + 65021^2 .

It is not an unprimeable number, because it can be changed into a prime (643666253641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160916563409 + ... + 160916563412.

Almost surely, 2^643666253642 is an apocalyptic number.

643666253642 is a deficient number, since it is larger than the sum of its proper divisors (321833126824).

643666253642 is a wasteful number, since it uses less digits than its factorization.

643666253642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321833126823.

The product of its digits is 22394880, while the sum is 53.

The spelling of 643666253642 in words is "six hundred forty-three billion, six hundred sixty-six million, two hundred fifty-three thousand, six hundred forty-two".