21259166781 has 4 divisors (see below), whose sum is σ = 28345555712. Its totient is φ = 14172777852.

The previous prime is 21259166771. The next prime is 21259166809. The reversal of 21259166781 is 18766195212.

It is a happy number.

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 not a de Polignac number, because 21259166781 - 2⁶ = 21259166717 is a prime.

It is a super-2 number, since 2×21259166781² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21259166781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21259166711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3543194461 + ... + 3543194466.

It is an arithmetic number, because the mean of its divisors is an integer number (7086388928).

Almost surely, 2^21259166781 is an apocalyptic number.

It is an amenable number.

21259166781 is a deficient number, since it is larger than the sum of its proper divisors (7086388931).

21259166781 is an equidigital number, since it uses as much as digits as its factorization.

21259166781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7086388930.

The product of its digits is 362880, while the sum is 48.

The spelling of 21259166781 in words is "twenty-one billion, two hundred fifty-nine million, one hundred sixty-six thousand, seven hundred eighty-one".