21689893 has 2 divisors, whose sum is σ = 21689894. Its totient is φ = 21689892.

The previous prime is 21689867. The next prime is 21689903. The reversal of 21689893 is 39898612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11716929 + 9972964 = 3423^2 + 3158^2 .

It is a cyclic number.

It is not a de Polignac number, because 21689893 - 2¹³ = 21681701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21689803) 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, 10844946 + 10844947.

It is an arithmetic number, because the mean of its divisors is an integer number (10844947).

Almost surely, 2^21689893 is an apocalyptic number.

It is an amenable number.

21689893 is a deficient number, since it is larger than the sum of its proper divisors (1).

21689893 is an equidigital number, since it uses as much as digits as its factorization.

21689893 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 186624, while the sum is 46.

The square root of 21689893 is about 4657.2409214040. The cubic root of 21689893 is about 278.8811345165.

It can be divided in two parts, 216 and 89893, that added together give a palindrome (90109).

The spelling of 21689893 in words is "twenty-one million, six hundred eighty-nine thousand, eight hundred ninety-three".