21278361536981 has 2 divisors, whose sum is σ = 21278361536982. Its totient is φ = 21278361536980.

The previous prime is 21278361536969. The next prime is 21278361537031. The reversal of 21278361536981 is 18963516387212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20105762763025 + 1172598773956 = 4483945^2 + 1082866^2 .

It is a cyclic number.

It is not a de Polignac number, because 21278361536981 - 2⁴² = 16880315025877 is a prime.

It is a super-2 number, since 2×21278361536981² (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 (21278361536941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639180768490 + 10639180768491.

It is an arithmetic number, because the mean of its divisors is an integer number (10639180768491).

Almost surely, 2^{21278361536981} is an apocalyptic number.

It is an amenable number.

21278361536981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21278361536981 is an equidigital number, since it uses as much as digits as its factorization.

21278361536981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 26127360, while the sum is 62.

The spelling of 21278361536981 in words is "twenty-one trillion, two hundred seventy-eight billion, three hundred sixty-one million, five hundred thirty-six thousand, nine hundred eighty-one".