21360826781 has 4 divisors (see below), whose sum is σ = 24412373472. Its totient is φ = 18309280092.

The previous prime is 21360826733. The next prime is 21360826793. The reversal of 21360826781 is 18762806312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21360826781 - 2¹⁸ = 21360564637 is a prime.

It is a super-2 number, since 2×21360826781² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21360826181) 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 in 3 ways as a sum of consecutive naturals, for example, 1525773335 + ... + 1525773348.

It is an arithmetic number, because the mean of its divisors is an integer number (6103093368).

Almost surely, 2^21360826781 is an apocalyptic number.

It is an amenable number.

21360826781 is a deficient number, since it is larger than the sum of its proper divisors (3051546691).

21360826781 is an equidigital number, since it uses as much as digits as its factorization.

21360826781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3051546690.

The product of its (nonzero) digits is 193536, while the sum is 44.

The spelling of 21360826781 in words is "twenty-one billion, three hundred sixty million, eight hundred twenty-six thousand, seven hundred eighty-one".