1643645345021 has 4 divisors (see below), whose sum is σ = 1643817518112. Its totient is φ = 1643473171932.

The previous prime is 1643645344993. The next prime is 1643645345033. The reversal of 1643645345021 is 1205435463461.

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.

It is a cyclic number.

It is not a de Polignac number, because 1643645345021 - 2¹⁰ = 1643645343997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1643645345071) 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, 86072225 + ... + 86091318.

It is an arithmetic number, because the mean of its divisors is an integer number (410954379528).

Almost surely, 2^{1643645345021} is an apocalyptic number.

It is an amenable number.

1643645345021 is a deficient number, since it is larger than the sum of its proper divisors (172173091).

1643645345021 is an equidigital number, since it uses as much as digits as its factorization.

1643645345021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172173090.

The product of its (nonzero) digits is 1036800, while the sum is 44.

The spelling of 1643645345021 in words is "one trillion, six hundred forty-three billion, six hundred forty-five million, three hundred forty-five thousand, twenty-one".