21605357232989 has 2 divisors, whose sum is σ = 21605357232990. Its totient is φ = 21605357232988.

The previous prime is 21605357232889. The next prime is 21605357233003. The reversal of 21605357232989 is 98923275350612.

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., 20514830248900 + 1090526984089 = 4529330^2 + 1044283^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21605357232989 is a prime.

It is a super-2 number, since 2×21605357232989² (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 (21605357232289) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802678616494 + 10802678616495.

It is an arithmetic number, because the mean of its divisors is an integer number (10802678616495).

Almost surely, 2^{21605357232989} is an apocalyptic number.

It is an amenable number.

21605357232989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605357232989 is an equidigital number, since it uses as much as digits as its factorization.

21605357232989 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48988800, while the sum is 62.

The spelling of 21605357232989 in words is "twenty-one trillion, six hundred five billion, three hundred fifty-seven million, two hundred thirty-two thousand, nine hundred eighty-nine".