21124657 has 2 divisors, whose sum is σ = 21124658. Its totient is φ = 21124656.

The previous prime is 21124643. The next prime is 21124661. The reversal of 21124657 is 75642112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14447601 + 6677056 = 3801^2 + 2584^2 .

It is a cyclic number.

It is not a de Polignac number, because 21124657 - 2⁷ = 21124529 is a prime.

It is a super-2 number, since 2×21124657² = 892502266735298, which contains 22 as substring.

It is equal to p_1337356 and since 21124657 and 1337356 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21124627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10562328 + 10562329.

It is an arithmetic number, because the mean of its divisors is an integer number (10562329).

Almost surely, 2^21124657 is an apocalyptic number.

It is an amenable number.

21124657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21124657 is an equidigital number, since it uses as much as digits as its factorization.

21124657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3360, while the sum is 28.

The square root of 21124657 is about 4596.1567640802. The cubic root of 21124657 is about 276.4372445261.

Adding to 21124657 its reverse (75642112), we get a palindrome (96766769).

The spelling of 21124657 in words is "twenty-one million, one hundred twenty-four thousand, six hundred fifty-seven".