21267738181 has 4 divisors (see below), whose sum is σ = 21343424364. Its totient is φ = 21192052000.

The previous prime is 21267738169. The next prime is 21267738211. The reversal of 21267738181 is 18183776212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12612413025 + 8655325156 = 112305^2 + 93034^2 .

It is a cyclic number.

It is not a de Polignac number, because 21267738181 - 2²¹ = 21265641029 is a prime.

It is a super-2 number, since 2×21267738181² (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 (21267738281) 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, 37842670 + ... + 37843231.

It is an arithmetic number, because the mean of its divisors is an integer number (5335856091).

Almost surely, 2^21267738181 is an apocalyptic number.

It is an amenable number.

21267738181 is a deficient number, since it is larger than the sum of its proper divisors (75686183).

21267738181 is an equidigital number, since it uses as much as digits as its factorization.

21267738181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75686182.

The product of its digits is 225792, while the sum is 46.

The spelling of 21267738181 in words is "twenty-one billion, two hundred sixty-seven million, seven hundred thirty-eight thousand, one hundred eighty-one".