21187273813 has 2 divisors, whose sum is σ = 21187273814. Its totient is φ = 21187273812.

The previous prime is 21187273769. The next prime is 21187273819. The reversal of 21187273813 is 31837278112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21175488324 + 11785489 = 145518^2 + 3433^2 .

It is a cyclic number.

It is not a de Polignac number, because 21187273813 - 2²⁵ = 21153719381 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21187273813.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21187273819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10593636906 + 10593636907.

It is an arithmetic number, because the mean of its divisors is an integer number (10593636907).

Almost surely, 2^21187273813 is an apocalyptic number.

It is an amenable number.

21187273813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21187273813 is an equidigital number, since it uses as much as digits as its factorization.

21187273813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 112896, while the sum is 43.

The spelling of 21187273813 in words is "twenty-one billion, one hundred eighty-seven million, two hundred seventy-three thousand, eight hundred thirteen".