21200657 has 4 divisors (see below), whose sum is σ = 21210480. Its totient is φ = 21190836.

The previous prime is 21200639. The next prime is 21200681. The reversal of 21200657 is 75600212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21200657 - 2⁸ = 21200401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21200617) 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 in 3 ways as a sum of consecutive naturals, for example, 107 + ... + 6512.

It is an arithmetic number, because the mean of its divisors is an integer number (5302620).

Almost surely, 2^21200657 is an apocalyptic number.

It is an amenable number.

21200657 is a deficient number, since it is larger than the sum of its proper divisors (9823).

21200657 is an equidigital number, since it uses as much as digits as its factorization.

21200657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9822.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 21200657 is about 4604.4171183767. The cubic root of 21200657 is about 276.7683597392.

Adding to 21200657 its reverse (75600212), we get a palindrome (96800869).

The spelling of 21200657 in words is "twenty-one million, two hundred thousand, six hundred fifty-seven".