21257349 has 4 divisors (see below), whose sum is σ = 28343136. Its totient is φ = 14171564.

The previous prime is 21257347. The next prime is 21257407. The reversal of 21257349 is 94375212.

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.

It is a cyclic number.

It is not a de Polignac number, because 21257349 - 2¹ = 21257347 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257347) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3542889 + ... + 3542894.

It is an arithmetic number, because the mean of its divisors is an integer number (7085784).

Almost surely, 2^21257349 is an apocalyptic number.

It is an amenable number.

21257349 is a deficient number, since it is larger than the sum of its proper divisors (7085787).

21257349 is an equidigital number, since it uses as much as digits as its factorization.

21257349 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7085786.

The product of its digits is 15120, while the sum is 33.

The square root of 21257349 is about 4610.5692707083. The cubic root of 21257349 is about 277.0148393133.

The spelling of 21257349 in words is "twenty-one million, two hundred fifty-seven thousand, three hundred forty-nine".