20490538721 has 8 divisors (see below), whose sum is σ = 20704494888. Its totient is φ = 20276800000.

The previous prime is 20490538711. The next prime is 20490538741. The reversal of 20490538721 is 12783509402.

It can be written as a sum of positive squares in 4 ways, for example, as 5078557696 + 15411981025 = 71264^2 + 124145^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20490538721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20490538711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 138641 + ... + 245361.

It is an arithmetic number, because the mean of its divisors is an integer number (2588061861).

Almost surely, 2^20490538721 is an apocalyptic number.

It is an amenable number.

20490538721 is a deficient number, since it is larger than the sum of its proper divisors (213956167).

20490538721 is a wasteful number, since it uses less digits than its factorization.

20490538721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108723.

The product of its (nonzero) digits is 120960, while the sum is 41.

The spelling of 20490538721 in words is "twenty billion, four hundred ninety million, five hundred thirty-eight thousand, seven hundred twenty-one".