13217721 has 16 divisors (see below), whose sum is σ = 20357568. Its totient is φ = 7539200.

The previous prime is 13217717. The next prime is 13217731. The reversal of 13217721 is 12771231.

It is a cyclic number.

It is not a de Polignac number, because 13217721 - 2² = 13217717 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 13217691 and 13217700.

It is not an unprimeable number, because it can be changed into a prime (13217731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11220 + ... + 12341.

It is an arithmetic number, because the mean of its divisors is an integer number (1272348).

Almost surely, 2^13217721 is an apocalyptic number.

13217721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

13217721 is a deficient number, since it is larger than the sum of its proper divisors (7139847).

13217721 is a wasteful number, since it uses less digits than its factorization.

13217721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23592.

The product of its digits is 588, while the sum is 24.

The square root of 13217721 is about 3635.6183793132. The cubic root of 13217721 is about 236.4388618862.

Adding to 13217721 its reverse (12771231), we get a palindrome (25988952).

The spelling of 13217721 in words is "thirteen million, two hundred seventeen thousand, seven hundred twenty-one".