21251347 has 4 divisors (see below), whose sum is σ = 22886080. Its totient is φ = 19616616.

The previous prime is 21251339. The next prime is 21251353. The reversal of 21251347 is 74315212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21251347 - 2³ = 21251339 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21251327) 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, 817347 + ... + 817372.

It is an arithmetic number, because the mean of its divisors is an integer number (5721520).

Almost surely, 2^21251347 is an apocalyptic number.

21251347 is a deficient number, since it is larger than the sum of its proper divisors (1634733).

21251347 is a wasteful number, since it uses less digits than its factorization.

21251347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1634732.

The product of its digits is 1680, while the sum is 25.

The square root of 21251347 is about 4609.9183289946. The cubic root of 21251347 is about 276.9887652001.

Adding to 21251347 its reverse (74315212), we get a palindrome (95566559).

The spelling of 21251347 in words is "twenty-one million, two hundred fifty-one thousand, three hundred forty-seven".