21147131 has 4 divisors (see below), whose sum is σ = 21277032. Its totient is φ = 21017232.

The previous prime is 21147127. The next prime is 21147157. The reversal of 21147131 is 13174112.

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 21147131 - 2² = 21147127 is a prime.

It is a super-2 number, since 2×21147131² = 894402299062322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21149131) 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, 64706 + ... + 65031.

It is an arithmetic number, because the mean of its divisors is an integer number (5319258).

Almost surely, 2^21147131 is an apocalyptic number.

21147131 is a deficient number, since it is larger than the sum of its proper divisors (129901).

21147131 is a wasteful number, since it uses less digits than its factorization.

21147131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129900.

The product of its digits is 168, while the sum is 20.

The square root of 21147131 is about 4598.6009829077. The cubic root of 21147131 is about 276.5352413642.

The spelling of 21147131 in words is "twenty-one million, one hundred forty-seven thousand, one hundred thirty-one".