13720221 has 6 divisors (see below), whose sum is σ = 19818110. Its totient is φ = 9146808.

The previous prime is 13720211. The next prime is 13720247. The reversal of 13720221 is 12202731.

It can be written as a sum of positive squares in only one way, i.e., 11799225 + 1920996 = 3435^2 + 1386^2 .

It is not a de Polignac number, because 13720221 - 2¹³ = 13712029 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 13720194 and 13720203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (13720211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 762226 + ... + 762243.

Almost surely, 2^13720221 is an apocalyptic number.

It is an amenable number.

13720221 is a deficient number, since it is larger than the sum of its proper divisors (6097889).

13720221 is a wasteful number, since it uses less digits than its factorization.

13720221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1524475 (or 1524472 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 13720221 is about 3704.0816675662. The cubic root of 13720221 is about 239.3979179179.

Adding to 13720221 its reverse (12202731), we get a palindrome (25922952).

The spelling of 13720221 in words is "thirteen million, seven hundred twenty thousand, two hundred twenty-one".