21153257 has 2 divisors, whose sum is σ = 21153258. Its totient is φ = 21153256.

The previous prime is 21153227. The next prime is 21153259. The reversal of 21153257 is 75235112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19855936 + 1297321 = 4456^2 + 1139^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21153257 is a prime.

Together with 21153259, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21153259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10576628 + 10576629.

It is an arithmetic number, because the mean of its divisors is an integer number (10576629).

Almost surely, 2^21153257 is an apocalyptic number.

It is an amenable number.

21153257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21153257 is an equidigital number, since it uses as much as digits as its factorization.

21153257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2100, while the sum is 26.

The square root of 21153257 is about 4599.2670068175. The cubic root of 21153257 is about 276.5619414610.

Adding to 21153257 its reverse (75235112), we get a palindrome (96388369).

The spelling of 21153257 in words is "twenty-one million, one hundred fifty-three thousand, two hundred fifty-seven".