21520734536989 has 2 divisors, whose sum is σ = 21520734536990. Its totient is φ = 21520734536988.

The previous prime is 21520734536941. The next prime is 21520734537077. The reversal of 21520734536989 is 98963543702512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21270009011364 + 250725525625 = 4611942^2 + 500725^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520734536989 - 2²¹ = 21520732439837 is a prime.

It is a super-2 number, since 2×21520734536989² (a number of 27 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21520734536989.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21520734536909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760367268494 + 10760367268495.

It is an arithmetic number, because the mean of its divisors is an integer number (10760367268495).

It is a 1-persistent number, because it is pandigital, but 2⋅21520734536989 = 43041469073978 is not.

Almost surely, 2^{21520734536989} is an apocalyptic number.

It is an amenable number.

21520734536989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520734536989 is an equidigital number, since it uses as much as digits as its factorization.

21520734536989 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 97977600, while the sum is 64.

The spelling of 21520734536989 in words is "twenty-one trillion, five hundred twenty billion, seven hundred thirty-four million, five hundred thirty-six thousand, nine hundred eighty-nine".