21654197 has 2 divisors, whose sum is σ = 21654198. Its totient is φ = 21654196.

The previous prime is 21654187. The next prime is 21654203. The reversal of 21654197 is 79145612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20151121 + 1503076 = 4489^2 + 1226^2 .

It is a cyclic number.

It is not a de Polignac number, because 21654197 - 2⁴ = 21654181 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21654187) 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 as a sum of consecutive naturals, namely, 10827098 + 10827099.

It is an arithmetic number, because the mean of its divisors is an integer number (10827099).

Almost surely, 2^21654197 is an apocalyptic number.

It is an amenable number.

21654197 is a deficient number, since it is larger than the sum of its proper divisors (1).

21654197 is an equidigital number, since it uses as much as digits as its factorization.

21654197 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15120, while the sum is 35.

The square root of 21654197 is about 4653.4070314126. The cubic root of 21654197 is about 278.7280615765.

The spelling of 21654197 in words is "twenty-one million, six hundred fifty-four thousand, one hundred ninety-seven".