21432729649 has 2 divisors, whose sum is σ = 21432729650. Its totient is φ = 21432729648.

The previous prime is 21432729599. The next prime is 21432729667. The reversal of 21432729649 is 94692723412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20109225249 + 1323504400 = 141807^2 + 36380^2 .

It is a cyclic number.

It is not a de Polignac number, because 21432729649 - 2¹¹ = 21432727601 is a prime.

It is not a weakly prime, because it can be changed into another prime (21432729349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10716364824 + 10716364825.

It is an arithmetic number, because the mean of its divisors is an integer number (10716364825).

Almost surely, 2^21432729649 is an apocalyptic number.

It is an amenable number.

21432729649 is a deficient number, since it is larger than the sum of its proper divisors (1).

21432729649 is an equidigital number, since it uses as much as digits as its factorization.

21432729649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1306368, while the sum is 49.

The spelling of 21432729649 in words is "twenty-one billion, four hundred thirty-two million, seven hundred twenty-nine thousand, six hundred forty-nine".