21257345 has 8 divisors (see below), whose sum is σ = 25643520. Its totient is φ = 16916080.

The previous prime is 21257323. The next prime is 21257347. The reversal of 21257345 is 54375212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21257345 - 2⁶ = 21257281 is a prime.

It is a Curzon 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 7 ways as a sum of consecutive naturals, for example, 10175 + ... + 12084.

It is an arithmetic number, because the mean of its divisors is an integer number (3205440).

Almost surely, 2^21257345 is an apocalyptic number.

It is an amenable number.

21257345 is a deficient number, since it is larger than the sum of its proper divisors (4386175).

21257345 is a wasteful number, since it uses less digits than its factorization.

21257345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22455.

The product of its digits is 8400, while the sum is 29.

The square root of 21257345 is about 4610.5688369224. The cubic root of 21257345 is about 277.0148219380.

The spelling of 21257345 in words is "twenty-one million, two hundred fifty-seven thousand, three hundred forty-five".