21047831 has 8 divisors (see below), whose sum is σ = 24087840. Its totient is φ = 18016128.

The previous prime is 21047827. The next prime is 21047833. The reversal of 21047831 is 13874012.

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 21047831 - 2² = 21047827 is a prime.

It is a super-2 number, since 2×21047831² = 886022379609122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21047831.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21047833) 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, 4955 + ... + 8163.

It is an arithmetic number, because the mean of its divisors is an integer number (3010980).

Almost surely, 2^21047831 is an apocalyptic number.

21047831 is a deficient number, since it is larger than the sum of its proper divisors (3040009).

21047831 is an equidigital number, since it uses as much as digits as its factorization.

21047831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4153.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21047831 is about 4587.7915166232. The cubic root of 21047831 is about 276.1017224640.

The spelling of 21047831 in words is "twenty-one million, forty-seven thousand, eight hundred thirty-one".