21691185629 has 2 divisors, whose sum is σ = 21691185630. Its totient is φ = 21691185628.

The previous prime is 21691185563. The next prime is 21691185653. The reversal of 21691185629 is 92658119612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18280392025 + 3410793604 = 135205^2 + 58402^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21691185629 is a prime.

It is a super-2 number, since 2×21691185629² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21691115629) 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, 10845592814 + 10845592815.

It is an arithmetic number, because the mean of its divisors is an integer number (10845592815).

Almost surely, 2^21691185629 is an apocalyptic number.

It is an amenable number.

21691185629 is a deficient number, since it is larger than the sum of its proper divisors (1).

21691185629 is an equidigital number, since it uses as much as digits as its factorization.

21691185629 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 466560, while the sum is 50.

The spelling of 21691185629 in words is "twenty-one billion, six hundred ninety-one million, one hundred eighty-five thousand, six hundred twenty-nine".