13215821 has 2 divisors, whose sum is σ = 13215822. Its totient is φ = 13215820.

The previous prime is 13215809. The next prime is 13215859. The reversal of 13215821 is 12851231.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10797796 + 2418025 = 3286^2 + 1555^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-13215821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13215871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6607910 + 6607911.

It is an arithmetic number, because the mean of its divisors is an integer number (6607911).

Almost surely, 2^13215821 is an apocalyptic number.

It is an amenable number.

13215821 is a deficient number, since it is larger than the sum of its proper divisors (1).

13215821 is an equidigital number, since it uses as much as digits as its factorization.

13215821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 480, while the sum is 23.

The square root of 13215821 is about 3635.3570663691. The cubic root of 13215821 is about 236.4275322638.

The spelling of 13215821 in words is "thirteen million, two hundred fifteen thousand, eight hundred twenty-one".