21266563361 has 4 divisors (see below), whose sum is σ = 21341710512. Its totient is φ = 21191416212.

The previous prime is 21266563349. The next prime is 21266563387. The reversal of 21266563361 is 16336566212.

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 a de Polignac number, because none of the positive numbers 2^k-21266563361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21266563391) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37573151 + ... + 37573716.

It is an arithmetic number, because the mean of its divisors is an integer number (5335427628).

Almost surely, 2^21266563361 is an apocalyptic number.

It is an amenable number.

21266563361 is a deficient number, since it is larger than the sum of its proper divisors (75147151).

21266563361 is an equidigital number, since it uses as much as digits as its factorization.

21266563361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75147150.

The product of its digits is 233280, while the sum is 41.

The spelling of 21266563361 in words is "twenty-one billion, two hundred sixty-six million, five hundred sixty-three thousand, three hundred sixty-one".