21335173 has 2 divisors, whose sum is σ = 21335174. Its totient is φ = 21335172.

The previous prime is 21335143. The next prime is 21335179. The reversal of 21335173 is 37153312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16916769 + 4418404 = 4113^2 + 2102^2 .

It is a cyclic number.

It is not a de Polignac number, because 21335173 - 2⁵ = 21335141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21335179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10667586 + 10667587.

It is an arithmetic number, because the mean of its divisors is an integer number (10667587).

Almost surely, 2^21335173 is an apocalyptic number.

It is an amenable number.

21335173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21335173 is an equidigital number, since it uses as much as digits as its factorization.

21335173 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1890, while the sum is 25.

The square root of 21335173 is about 4619.0012989823. The cubic root of 21335173 is about 277.3524817213.

Adding to 21335173 its reverse (37153312), we get a palindrome (58488485).

The spelling of 21335173 in words is "twenty-one million, three hundred thirty-five thousand, one hundred seventy-three".