21700237 has 4 divisors (see below), whose sum is σ = 23369500. Its totient is φ = 20030976.

The previous prime is 21700219. The next prime is 21700243. The reversal of 21700237 is 73200712.

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 2172676 + 19527561 = 1474^2 + 4419^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21700237 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21700297) 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 in 3 ways as a sum of consecutive naturals, for example, 834612 + ... + 834637.

It is an arithmetic number, because the mean of its divisors is an integer number (5842375).

Almost surely, 2^21700237 is an apocalyptic number.

It is an amenable number.

21700237 is a deficient number, since it is larger than the sum of its proper divisors (1669263).

21700237 is a wasteful number, since it uses less digits than its factorization.

21700237 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1669262.

The product of its (nonzero) digits is 588, while the sum is 22.

The square root of 21700237 is about 4658.3513177947. The cubic root of 21700237 is about 278.9254606610.

Adding to 21700237 its reverse (73200712), we get a palindrome (94900949).

The spelling of 21700237 in words is "twenty-one million, seven hundred thousand, two hundred thirty-seven".