21742085 has 4 divisors (see below), whose sum is σ = 26090508. Its totient is φ = 17393664.

The previous prime is 21742043. The next prime is 21742087. The reversal of 21742085 is 58024712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9132484 + 12609601 = 3022^2 + 3551^2 .

It is a cyclic number.

It is not a de Polignac number, because 21742085 - 2²⁰ = 20693509 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21742087) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2174204 + ... + 2174213.

It is an arithmetic number, because the mean of its divisors is an integer number (6522627).

Almost surely, 2^21742085 is an apocalyptic number.

It is an amenable number.

21742085 is a deficient number, since it is larger than the sum of its proper divisors (4348423).

21742085 is an equidigital number, since it uses as much as digits as its factorization.

21742085 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4348422.

The product of its (nonzero) digits is 4480, while the sum is 29.

The square root of 21742085 is about 4662.8408722580. The cubic root of 21742085 is about 279.1046442250.

Adding to 21742085 its reverse (58024712), we get a palindrome (79766797).

The spelling of 21742085 in words is "twenty-one million, seven hundred forty-two thousand, eighty-five".