21116257 has 2 divisors, whose sum is σ = 21116258. Its totient is φ = 21116256.

The previous prime is 21116219. The next prime is 21116267. The reversal of 21116257 is 75261112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20784481 + 331776 = 4559^2 + 576^2 .

It is a cyclic number.

It is not a de Polignac number, because 21116257 - 2¹¹ = 21114209 is a prime.

It is not a weakly prime, because it can be changed into another prime (21116267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10558128 + 10558129.

It is an arithmetic number, because the mean of its divisors is an integer number (10558129).

Almost surely, 2^21116257 is an apocalyptic number.

It is an amenable number.

21116257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21116257 is an equidigital number, since it uses as much as digits as its factorization.

21116257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 840, while the sum is 25.

The square root of 21116257 is about 4595.2428662694. The cubic root of 21116257 is about 276.4005988707.

Adding to 21116257 its reverse (75261112), we get a palindrome (96377369).

The spelling of 21116257 in words is "twenty-one million, one hundred sixteen thousand, two hundred fifty-seven".