21023237 has 4 divisors (see below), whose sum is σ = 22259916. Its totient is φ = 19786560.

The previous prime is 21023213. The next prime is 21023257. The reversal of 21023237 is 73232012.

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 17522596 + 3500641 = 4186^2 + 1871^2 .

It is a cyclic number.

It is not a de Polignac number, because 21023237 - 2¹⁰ = 21022213 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 (21023207) 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, 618314 + ... + 618347.

It is an arithmetic number, because the mean of its divisors is an integer number (5564979).

Almost surely, 2^21023237 is an apocalyptic number.

It is an amenable number.

21023237 is a deficient number, since it is larger than the sum of its proper divisors (1236679).

21023237 is a wasteful number, since it uses less digits than its factorization.

21023237 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1236678.

The product of its (nonzero) digits is 504, while the sum is 20.

The square root of 21023237 is about 4585.1103585410. The cubic root of 21023237 is about 275.9941406374.

Adding to 21023237 its reverse (73232012), we get a palindrome (94255249).

The spelling of 21023237 in words is "twenty-one million, twenty-three thousand, two hundred thirty-seven".