21237145 has 4 divisors (see below), whose sum is σ = 25484580. Its totient is φ = 16989712.

The previous prime is 21237143. The next prime is 21237157. The reversal of 21237145 is 54173212.

It is a happy number.

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 7907344 + 13329801 = 2812^2 + 3651^2 .

It is a cyclic number.

It is not a de Polignac number, because 21237145 - 2¹ = 21237143 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21237143) 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, 2123710 + ... + 2123719.

It is an arithmetic number, because the mean of its divisors is an integer number (6371145).

Almost surely, 2^21237145 is an apocalyptic number.

It is an amenable number.

21237145 is a deficient number, since it is larger than the sum of its proper divisors (4247435).

21237145 is an equidigital number, since it uses as much as digits as its factorization.

21237145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4247434.

The product of its digits is 1680, while the sum is 25.

The square root of 21237145 is about 4608.3776971945. The cubic root of 21237145 is about 276.9270487817.

The spelling of 21237145 in words is "twenty-one million, two hundred thirty-seven thousand, one hundred forty-five".