21731147 has 2 divisors, whose sum is σ = 21731148. Its totient is φ = 21731146.

The previous prime is 21731141. The next prime is 21731161. The reversal of 21731147 is 74113712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21731147 - 2⁴ = 21731131 is a prime.

It is not a weakly prime, because it can be changed into another prime (21731141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865573 + 10865574.

It is an arithmetic number, because the mean of its divisors is an integer number (10865574).

Almost surely, 2^21731147 is an apocalyptic number.

21731147 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731147 is an equidigital number, since it uses as much as digits as its factorization.

21731147 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1176, while the sum is 26.

The square root of 21731147 is about 4661.6678345845. The cubic root of 21731147 is about 279.0578324207.

Adding to 21731147 its reverse (74113712), we get a palindrome (95844859).

The spelling of 21731147 in words is "twenty-one million, seven hundred thirty-one thousand, one hundred forty-seven".