21235657 has 2 divisors, whose sum is σ = 21235658. Its totient is φ = 21235656.

The previous prime is 21235639. The next prime is 21235723. The reversal of 21235657 is 75653212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10634121 + 10601536 = 3261^2 + 3256^2 .

It is a cyclic number.

It is not a de Polignac number, because 21235657 - 2¹¹ = 21233609 is a prime.

It is not a weakly prime, because it can be changed into another prime (21235607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617828 + 10617829.

It is an arithmetic number, because the mean of its divisors is an integer number (10617829).

Almost surely, 2^21235657 is an apocalyptic number.

It is an amenable number.

21235657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21235657 is an equidigital number, since it uses as much as digits as its factorization.

21235657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12600, while the sum is 31.

The square root of 21235657 is about 4608.2162492661. The cubic root of 21235657 is about 276.9205809149.

Adding to 21235657 its reverse (75653212), we get a palindrome (96888869).

The spelling of 21235657 in words is "twenty-one million, two hundred thirty-five thousand, six hundred fifty-seven".