21361531247 has 4 divisors (see below), whose sum is σ = 24413178576. Its totient is φ = 18309883920.

The previous prime is 21361531241. The next prime is 21361531273. The reversal of 21361531247 is 74213516312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21361531247 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 (21361531241) 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, 1525823654 + ... + 1525823667.

It is an arithmetic number, because the mean of its divisors is an integer number (6103294644).

Almost surely, 2^21361531247 is an apocalyptic number.

21361531247 is a deficient number, since it is larger than the sum of its proper divisors (3051647329).

21361531247 is an equidigital number, since it uses as much as digits as its factorization.

21361531247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3051647328.

The product of its digits is 30240, while the sum is 35.

The spelling of 21361531247 in words is "twenty-one billion, three hundred sixty-one million, five hundred thirty-one thousand, two hundred forty-seven".