21101257 has 2 divisors, whose sum is σ = 21101258. Its totient is φ = 21101256.

The previous prime is 21101251. The next prime is 21101263. The reversal of 21101257 is 75210112.

It is a balanced prime because it is at equal distance from previous prime (21101251) and next prime (21101263).

It can be written as a sum of positive squares in only one way, i.e., 13461561 + 7639696 = 3669^2 + 2764^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21101257 is a prime.

It is not a weakly prime, because it can be changed into another prime (21101251) 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, 10550628 + 10550629.

It is an arithmetic number, because the mean of its divisors is an integer number (10550629).

Almost surely, 2^21101257 is an apocalyptic number.

It is an amenable number.

21101257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101257 is an equidigital number, since it uses as much as digits as its factorization.

21101257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 21101257 is about 4593.6104536628. The cubic root of 21101257 is about 276.3351360209.

Adding to 21101257 its reverse (75210112), we get a palindrome (96311369).

The spelling of 21101257 in words is "twenty-one million, one hundred one thousand, two hundred fifty-seven".