21057349 has 4 divisors (see below), whose sum is σ = 21311136. Its totient is φ = 20803564.

The previous prime is 21057341. The next prime is 21057419. The reversal of 21057349 is 94375012.

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 21057349 - 2³ = 21057341 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21057349.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21057341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 126769 + ... + 126934.

It is an arithmetic number, because the mean of its divisors is an integer number (5327784).

Almost surely, 2^21057349 is an apocalyptic number.

It is an amenable number.

21057349 is a deficient number, since it is larger than the sum of its proper divisors (253787).

21057349 is an equidigital number, since it uses as much as digits as its factorization.

21057349 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 253786.

The product of its (nonzero) digits is 7560, while the sum is 31.

The square root of 21057349 is about 4588.8287176577. The cubic root of 21057349 is about 276.1433346721.

The spelling of 21057349 in words is "twenty-one million, fifty-seven thousand, three hundred forty-nine".