21275047 has 4 divisors (see below), whose sum is σ = 21566560. Its totient is φ = 20983536.

The previous prime is 21275039. The next prime is 21275053. The reversal of 21275047 is 74057212.

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 21275047 - 2³ = 21275039 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21275017) 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, 145647 + ... + 145792.

It is an arithmetic number, because the mean of its divisors is an integer number (5391640).

Almost surely, 2^21275047 is an apocalyptic number.

21275047 is a deficient number, since it is larger than the sum of its proper divisors (291513).

21275047 is an equidigital number, since it uses as much as digits as its factorization.

21275047 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291512.

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 21275047 is about 4612.4881571664. The cubic root of 21275047 is about 277.0916950662.

The spelling of 21275047 in words is "twenty-one million, two hundred seventy-five thousand, forty-seven".