13987721 has 6 divisors (see below), whose sum is σ = 15375066. Its totient is φ = 12716000.

The previous prime is 13987681. The next prime is 13987723. The reversal of 13987721 is 12778931.

It can be written as a sum of positive squares in only one way, i.e., 13987600 + 121 = 3740^2 + 11^2 .

It is not a de Polignac number, because 13987721 - 2¹⁰ = 13986697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13987723) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 57680 + ... + 57921.

It is an arithmetic number, because the mean of its divisors is an integer number (2562511).

Almost surely, 2^13987721 is an apocalyptic number.

13987721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

13987721 is a deficient number, since it is larger than the sum of its proper divisors (1387345).

13987721 is a wasteful number, since it uses less digits than its factorization.

13987721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115623 (or 115612 counting only the distinct ones).

The product of its digits is 21168, while the sum is 38.

The square root of 13987721 is about 3740.0161764356. The cubic root of 13987721 is about 240.9437435767.

It can be divided in two parts, 1398 and 7721, that added together give a palindrome (9119).

The spelling of 13987721 in words is "thirteen million, nine hundred eighty-seven thousand, seven hundred twenty-one".