21143257 has 16 divisors (see below), whose sum is σ = 23941440. Its totient is φ = 18551808.

The previous prime is 21143251. The next prime is 21143261. The reversal of 21143257 is 75234112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21143257 - 2¹⁵ = 21110489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21143251) 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 15 ways as a sum of consecutive naturals, for example, 21153 + ... + 22129.

It is an arithmetic number, because the mean of its divisors is an integer number (1496340).

Almost surely, 2^21143257 is an apocalyptic number.

It is an amenable number.

21143257 is a deficient number, since it is larger than the sum of its proper divisors (2798183).

21143257 is a wasteful number, since it uses less digits than its factorization.

21143257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1080.

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

The square root of 21143257 is about 4598.1797485527. The cubic root of 21143257 is about 276.5183539205.

Adding to 21143257 its reverse (75234112), we get a palindrome (96377369).

The spelling of 21143257 in words is "twenty-one million, one hundred forty-three thousand, two hundred fifty-seven".