21504642347 has 2 divisors, whose sum is σ = 21504642348. Its totient is φ = 21504642346.

The previous prime is 21504642331. The next prime is 21504642353. The reversal of 21504642347 is 74324640512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21504642347 - 2⁴ = 21504642331 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21504642347.

It is not a weakly prime, because it can be changed into another prime (21504642547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752321173 + 10752321174.

It is an arithmetic number, because the mean of its divisors is an integer number (10752321174).

Almost surely, 2^21504642347 is an apocalyptic number.

21504642347 is a deficient number, since it is larger than the sum of its proper divisors (1).

21504642347 is an equidigital number, since it uses as much as digits as its factorization.

21504642347 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 161280, while the sum is 38.

The spelling of 21504642347 in words is "twenty-one billion, five hundred four million, six hundred forty-two thousand, three hundred forty-seven".