21202720613 has 8 divisors (see below), whose sum is σ = 21935902680. Its totient is φ = 20469675520.

The previous prime is 21202720579. The next prime is 21202720709. The reversal of 21202720613 is 31602720212.

It can be written as a sum of positive squares in 4 ways, for example, as 11937310564 + 9265410049 = 109258^2 + 96257^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21202720613 - 2¹⁸ = 21202458469 is a prime.

It is a super-2 number, since 2×21202720613² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21202720213) 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 in 7 ways as a sum of consecutive naturals, for example, 356381 + ... + 411597.

It is an arithmetic number, because the mean of its divisors is an integer number (2741987835).

Almost surely, 2^21202720613 is an apocalyptic number.

It is an amenable number.

21202720613 is a deficient number, since it is larger than the sum of its proper divisors (733182067).

21202720613 is a wasteful number, since it uses less digits than its factorization.

21202720613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68487.

The product of its (nonzero) digits is 2016, while the sum is 26.

The spelling of 21202720613 in words is "twenty-one billion, two hundred two million, seven hundred twenty thousand, six hundred thirteen".