19623642821 has 4 divisors (see below), whose sum is σ = 19623926700. Its totient is φ = 19623358944.

The previous prime is 19623642811. The next prime is 19623642839. The reversal of 19623642821 is 12824632691.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 12591981796 + 7031661025 = 112214^2 + 83855^2 .

It is a cyclic number.

It is not a de Polignac number, because 19623642821 - 2¹⁴ = 19623626437 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 (19623642811) 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, 36665 + ... + 201473.

It is an arithmetic number, because the mean of its divisors is an integer number (4905981675).

Almost surely, 2^19623642821 is an apocalyptic number.

It is an amenable number.

19623642821 is a deficient number, since it is larger than the sum of its proper divisors (283879).

19623642821 is a wasteful number, since it uses less digits than its factorization.

19623642821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 283878.

The product of its digits is 248832, while the sum is 44.

The spelling of 19623642821 in words is "nineteen billion, six hundred twenty-three million, six hundred forty-two thousand, eight hundred twenty-one".