21661165739429 has 2 divisors, whose sum is σ = 21661165739430. Its totient is φ = 21661165739428.

The previous prime is 21661165739377. The next prime is 21661165739483. The reversal of 21661165739429 is 92493756116612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14487714150529 + 7173451588900 = 3806273^2 + 2678330^2 .

It is a cyclic number.

It is not a de Polignac number, because 21661165739429 - 2¹² = 21661165735333 is a prime.

It is a super-2 number, since 2×21661165739429² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21661165732429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830582869714 + 10830582869715.

It is an arithmetic number, because the mean of its divisors is an integer number (10830582869715).

Almost surely, 2^{21661165739429} is an apocalyptic number.

It is an amenable number.

21661165739429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661165739429 is an equidigital number, since it uses as much as digits as its factorization.

21661165739429 is an evil number, because the sum of its binary digits is even.

The product of its digits is 29393280, while the sum is 62.

The spelling of 21661165739429 in words is "twenty-one trillion, six hundred sixty-one billion, one hundred sixty-five million, seven hundred thirty-nine thousand, four hundred twenty-nine".