21849257 has 2 divisors, whose sum is σ = 21849258. Its totient is φ = 21849256.

The previous prime is 21849227. The next prime is 21849283. The reversal of 21849257 is 75294812.

21849257 is nontrivially palindromic in base 5.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21353641 + 495616 = 4621^2 + 704^2 .

It is a cyclic number.

It is not a de Polignac number, because 21849257 - 2¹⁶ = 21783721 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21849257.

It is not a weakly prime, because it can be changed into another prime (21849227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10924628 + 10924629.

It is an arithmetic number, because the mean of its divisors is an integer number (10924629).

Almost surely, 2^21849257 is an apocalyptic number.

It is an amenable number.

21849257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21849257 is an equidigital number, since it uses as much as digits as its factorization.

21849257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40320, while the sum is 38.

The square root of 21849257 is about 4674.3188808638. The cubic root of 21849257 is about 279.5624842301.

The spelling of 21849257 in words is "twenty-one million, eight hundred forty-nine thousand, two hundred fifty-seven".