21744157 has 2 divisors, whose sum is σ = 21744158. Its totient is φ = 21744156.

The previous prime is 21744143. The next prime is 21744161. The reversal of 21744157 is 75144712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17799961 + 3944196 = 4219^2 + 1986^2 .

It is a cyclic number.

It is not a de Polignac number, because 21744157 - 2²³ = 13355549 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21744137) 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 as a sum of consecutive naturals, namely, 10872078 + 10872079.

It is an arithmetic number, because the mean of its divisors is an integer number (10872079).

Almost surely, 2^21744157 is an apocalyptic number.

It is an amenable number.

21744157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21744157 is an equidigital number, since it uses as much as digits as its factorization.

21744157 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7840, while the sum is 31.

The square root of 21744157 is about 4663.0630491127. The cubic root of 21744157 is about 279.1135100790.

Adding to 21744157 its reverse (75144712), we get a palindrome (96888869).

The spelling of 21744157 in words is "twenty-one million, seven hundred forty-four thousand, one hundred fifty-seven".