13997821 has 2 divisors, whose sum is σ = 13997822. Its totient is φ = 13997820.

The previous prime is 13997801. The next prime is 13997827. The reversal of 13997821 is 12879931.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7080921 + 6916900 = 2661^2 + 2630^2 .

It is a cyclic number.

It is not a de Polignac number, because 13997821 - 2⁷ = 13997693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13997827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6998910 + 6998911.

It is an arithmetic number, because the mean of its divisors is an integer number (6998911).

Almost surely, 2^13997821 is an apocalyptic number.

It is an amenable number.

13997821 is a deficient number, since it is larger than the sum of its proper divisors (1).

13997821 is an equidigital number, since it uses as much as digits as its factorization.

13997821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 40.

The square root of 13997821 is about 3741.3661943199. The cubic root of 13997821 is about 241.0017217211.

The spelling of 13997821 in words is "thirteen million, nine hundred ninety-seven thousand, eight hundred twenty-one".