21072721069 has 2 divisors, whose sum is σ = 21072721070. Its totient is φ = 21072721068.

The previous prime is 21072721067. The next prime is 21072721091. The reversal of 21072721069 is 96012727012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20623832100 + 448888969 = 143610^2 + 21187^2 .

It is a cyclic number.

It is not a de Polignac number, because 21072721069 - 2¹ = 21072721067 is a prime.

It is a super-2 number, since 2×21072721069² (a number of 21 digits) contains 22 as substring.

Together with 21072721067, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21072721067) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10536360534 + 10536360535.

It is an arithmetic number, because the mean of its divisors is an integer number (10536360535).

Almost surely, 2^21072721069 is an apocalyptic number.

It is an amenable number.

21072721069 is a deficient number, since it is larger than the sum of its proper divisors (1).

21072721069 is an equidigital number, since it uses as much as digits as its factorization.

21072721069 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21168, while the sum is 37.

The spelling of 21072721069 in words is "twenty-one billion, seventy-two million, seven hundred twenty-one thousand, sixty-nine".