21354276781 has 2 divisors, whose sum is σ = 21354276782. Its totient is φ = 21354276780.

The previous prime is 21354276763. The next prime is 21354276821. The reversal of 21354276781 is 18767245312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19553547556 + 1800729225 = 139834^2 + 42435^2 .

It is a cyclic number.

It is not a de Polignac number, because 21354276781 - 2¹⁵ = 21354244013 is a prime.

It is a super-2 number, since 2×21354276781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21354216781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10677138390 + 10677138391.

It is an arithmetic number, because the mean of its divisors is an integer number (10677138391).

Almost surely, 2^21354276781 is an apocalyptic number.

It is an amenable number.

21354276781 is a deficient number, since it is larger than the sum of its proper divisors (1).

21354276781 is an equidigital number, since it uses as much as digits as its factorization.

21354276781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 564480, while the sum is 46.

The spelling of 21354276781 in words is "twenty-one billion, three hundred fifty-four million, two hundred seventy-six thousand, seven hundred eighty-one".