21371237 has 4 divisors (see below), whose sum is σ = 21948876. Its totient is φ = 20793600.

The previous prime is 21371201. The next prime is 21371239. The reversal of 21371237 is 73217312.

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 20784481 + 586756 = 4559^2 + 766^2 .

It is a cyclic number.

It is not a de Polignac number, because 21371237 - 2⁸ = 21370981 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 (21371239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 288764 + ... + 288837.

It is an arithmetic number, because the mean of its divisors is an integer number (5487219).

Almost surely, 2^21371237 is an apocalyptic number.

It is an amenable number.

21371237 is a deficient number, since it is larger than the sum of its proper divisors (577639).

21371237 is an equidigital number, since it uses as much as digits as its factorization.

21371237 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 577638.

The product of its digits is 1764, while the sum is 26.

The square root of 21371237 is about 4622.9035248424. The cubic root of 21371237 is about 277.5086683979.

Adding to 21371237 its reverse (73217312), we get a palindrome (94588549).

It can be divided in two parts, 213712 and 37, that multiplied together give a square (7907344 = 2812²).

The spelling of 21371237 in words is "twenty-one million, three hundred seventy-one thousand, two hundred thirty-seven".