21436688729 has 2 divisors, whose sum is σ = 21436688730. Its totient is φ = 21436688728.

The previous prime is 21436688723. The next prime is 21436688737. The reversal of 21436688729 is 92788663412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20541482329 + 895206400 = 143323^2 + 29920^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21436688729 is a prime.

It is not a weakly prime, because it can be changed into another prime (21436688723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10718344364 + 10718344365.

It is an arithmetic number, because the mean of its divisors is an integer number (10718344365).

Almost surely, 2^21436688729 is an apocalyptic number.

It is an amenable number.

21436688729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21436688729 is an equidigital number, since it uses as much as digits as its factorization.

21436688729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6967296, while the sum is 56.

The spelling of 21436688729 in words is "twenty-one billion, four hundred thirty-six million, six hundred eighty-eight thousand, seven hundred twenty-nine".