18723457421 has 2 divisors, whose sum is σ = 18723457422. Its totient is φ = 18723457420.

The previous prime is 18723457409. The next prime is 18723457429. The reversal of 18723457421 is 12475432781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10607970025 + 8115487396 = 102995^2 + 90086^2 .

It is a cyclic number.

It is not a de Polignac number, because 18723457421 - 2¹⁸ = 18723195277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18723457429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9361728710 + 9361728711.

It is an arithmetic number, because the mean of its divisors is an integer number (9361728711).

Almost surely, 2^18723457421 is an apocalyptic number.

It is an amenable number.

18723457421 is a deficient number, since it is larger than the sum of its proper divisors (1).

18723457421 is an equidigital number, since it uses as much as digits as its factorization.

18723457421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 376320, while the sum is 44.

The spelling of 18723457421 in words is "eighteen billion, seven hundred twenty-three million, four hundred fifty-seven thousand, four hundred twenty-one".