21231516247 has 2 divisors, whose sum is σ = 21231516248. Its totient is φ = 21231516246.

The previous prime is 21231516193. The next prime is 21231516253. The reversal of 21231516247 is 74261513212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21231516247 - 2³¹ = 19084032599 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21231516347) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615758123 + 10615758124.

It is an arithmetic number, because the mean of its divisors is an integer number (10615758124).

Almost surely, 2^21231516247 is an apocalyptic number.

21231516247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231516247 is an equidigital number, since it uses as much as digits as its factorization.

21231516247 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20160, while the sum is 34.

The spelling of 21231516247 in words is "twenty-one billion, two hundred thirty-one million, five hundred sixteen thousand, two hundred forty-seven".