21338278457 has 2 divisors, whose sum is σ = 21338278458. Its totient is φ = 21338278456.

The previous prime is 21338278411. The next prime is 21338278459. The reversal of 21338278457 is 75487283312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10684116496 + 10654161961 = 103364^2 + 103219^2 .

It is a cyclic number.

It is not a de Polignac number, because 21338278457 - 2²⁴ = 21321501241 is a prime.

Together with 21338278459, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21338278459) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10669139228 + 10669139229.

It is an arithmetic number, because the mean of its divisors is an integer number (10669139229).

Almost surely, 2^21338278457 is an apocalyptic number.

It is an amenable number.

21338278457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21338278457 is an equidigital number, since it uses as much as digits as its factorization.

21338278457 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2257920, while the sum is 50.

The spelling of 21338278457 in words is "twenty-one billion, three hundred thirty-eight million, two hundred seventy-eight thousand, four hundred fifty-seven".