21278857873477 has 2 divisors, whose sum is σ = 21278857873478. Its totient is φ = 21278857873476.

The previous prime is 21278857873397. The next prime is 21278857873489. The reversal of 21278857873477 is 77437875887212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19779002074881 + 1499855798596 = 4447359^2 + 1224686^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21278857873477 is a prime.

It is a super-2 number, since 2×21278857873477² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21278857876477) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639428936738 + 10639428936739.

It is an arithmetic number, because the mean of its divisors is an integer number (10639428936739).

Almost surely, 2^{21278857873477} is an apocalyptic number.

It is an amenable number.

21278857873477 is a deficient number, since it is larger than the sum of its proper divisors (1).

21278857873477 is an equidigital number, since it uses as much as digits as its factorization.

21278857873477 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2065244160, while the sum is 76.

The spelling of 21278857873477 in words is "twenty-one trillion, two hundred seventy-eight billion, eight hundred fifty-seven million, eight hundred seventy-three thousand, four hundred seventy-seven".