21931529729 has 2 divisors, whose sum is σ = 21931529730. Its totient is φ = 21931529728.

The previous prime is 21931529701. The next prime is 21931529803. The reversal of 21931529729 is 92792513912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11063884225 + 10867645504 = 105185^2 + 104248^2 .

It is a cyclic number.

It is not a de Polignac number, because 21931529729 - 2¹² = 21931525633 is a prime.

It is not a weakly prime, because it can be changed into another prime (21931129729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10965764864 + 10965764865.

It is an arithmetic number, because the mean of its divisors is an integer number (10965764865).

Almost surely, 2^21931529729 is an apocalyptic number.

It is an amenable number.

21931529729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21931529729 is an equidigital number, since it uses as much as digits as its factorization.

21931529729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 612360, while the sum is 50.

The spelling of 21931529729 in words is "twenty-one billion, nine hundred thirty-one million, five hundred twenty-nine thousand, seven hundred twenty-nine".