21057847 has 8 divisors (see below), whose sum is σ = 21890736. Its totient is φ = 20238912.

The previous prime is 21057821. The next prime is 21057877. The reversal of 21057847 is 74875012.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21057847 - 2¹¹ = 21055799 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 (21057877) 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 7 ways as a sum of consecutive naturals, for example, 358 + ... + 6499.

It is an arithmetic number, because the mean of its divisors is an integer number (2736342).

Almost surely, 2^21057847 is an apocalyptic number.

21057847 is a deficient number, since it is larger than the sum of its proper divisors (832889).

21057847 is an equidigital number, since it uses as much as digits as its factorization.

21057847 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6977.

The product of its (nonzero) digits is 15680, while the sum is 34.

The square root of 21057847 is about 4588.8829795496. The cubic root of 21057847 is about 276.1455115573.

It can be divided in two parts, 21057 and 847, that added together give a square (21904 = 148²).

The spelling of 21057847 in words is "twenty-one million, fifty-seven thousand, eight hundred forty-seven".