21307457 has 2 divisors, whose sum is σ = 21307458. Its totient is φ = 21307456.

The previous prime is 21307441. The next prime is 21307469. The reversal of 21307457 is 75470312.

It is a Cunningham number, because it is equal to 4616²+1.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21307456 + 1 = 4616^2 + 1^2 .

It is a cyclic number.

It is not a de Polignac number, because 21307457 - 2⁴ = 21307441 is a prime.

It is not a weakly prime, because it can be changed into another prime (21307487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10653728 + 10653729.

It is an arithmetic number, because the mean of its divisors is an integer number (10653729).

Almost surely, 2^21307457 is an apocalyptic number.

It is an amenable number.

21307457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21307457 is an equidigital number, since it uses as much as digits as its factorization.

21307457 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5880, while the sum is 29.

The square root of 21307457 is about 4616.0001083189. Note that the first 3 decimals coincide. The cubic root of 21307457 is about 277.2323290748.

Adding to 21307457 its reverse (75470312), we get a palindrome (96777769).

The spelling of 21307457 in words is "twenty-one million, three hundred seven thousand, four hundred fifty-seven".