13968639721 has 3 divisors (see below), whose sum is σ = 13968757911. Its totient is φ = 13968521532.

The previous prime is 13968639677. The next prime is 13968639761. The reversal of 13968639721 is 12793686931.

The square root of 13968639721 is 118189.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 13395516121 + 573123600 = 115739^2 + 23940^2 .

It is not a de Polignac number, because 13968639721 - 2¹³ = 13968631529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13968639761) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 59095 + ... + 177283.

It is an arithmetic number, because the mean of its divisors is an integer number (4656252637).

Almost surely, 2^13968639721 is an apocalyptic number.

13968639721 is the 118189-th square number.

13968639721 is the 59095-th centered octagonal number.

It is an amenable number.

13968639721 is a deficient number, since it is larger than the sum of its proper divisors (118190).

13968639721 is an frugal number, since it uses more digits than its factorization.

13968639721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236378 (or 118189 counting only the distinct ones).

The product of its digits is 2939328, while the sum is 55.

The spelling of 13968639721 in words is "thirteen billion, nine hundred sixty-eight million, six hundred thirty-nine thousand, seven hundred twenty-one".