21645703873 has 4 divisors (see below), whose sum is σ = 21647082240. Its totient is φ = 21644325508.

The previous prime is 21645703861. The next prime is 21645703889. The reversal of 21645703873 is 37830754612.

It is a happy number.

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 21645703873 - 2¹⁷ = 21645572801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21645700873) 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, 665353 + ... + 697126.

It is an arithmetic number, because the mean of its divisors is an integer number (5411770560).

Almost surely, 2^21645703873 is an apocalyptic number.

It is an amenable number.

21645703873 is a deficient number, since it is larger than the sum of its proper divisors (1378367).

21645703873 is a wasteful number, since it uses less digits than its factorization.

21645703873 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1378366.

The product of its (nonzero) digits is 846720, while the sum is 46.

The spelling of 21645703873 in words is "twenty-one billion, six hundred forty-five million, seven hundred three thousand, eight hundred seventy-three".