21278857873397 has 2 divisors, whose sum is σ = 21278857873398. Its totient is φ = 21278857873396.

The previous prime is 21278857873393. The next prime is 21278857873477. The reversal of 21278857873397 is 79337875887212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13498378872196 + 7780479001201 = 3674014^2 + 2789351^2 .

It is a cyclic number.

It is not a de Polignac number, because 21278857873397 - 2² = 21278857873393 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21278857873393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639428936698 + 10639428936699.

It is an arithmetic number, because the mean of its divisors is an integer number (10639428936699).

Almost surely, 2^{21278857873397} is an apocalyptic number.

It is an amenable number.

21278857873397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21278857873397 is an equidigital number, since it uses as much as digits as its factorization.

21278857873397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1991485440, while the sum is 77.

The spelling of 21278857873397 in words is "twenty-one trillion, two hundred seventy-eight billion, eight hundred fifty-seven million, eight hundred seventy-three thousand, three hundred ninety-seven".