21247171547 has 4 divisors (see below), whose sum is σ = 24282481776. Its totient is φ = 18211861320.

The previous prime is 21247171471. The next prime is 21247171559. The reversal of 21247171547 is 74517174212.

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 21247171547 - 2¹² = 21247167451 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21247173547) 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, 1517655104 + ... + 1517655117.

It is an arithmetic number, because the mean of its divisors is an integer number (6070620444).

Almost surely, 2^21247171547 is an apocalyptic number.

21247171547 is a deficient number, since it is larger than the sum of its proper divisors (3035310229).

21247171547 is an equidigital number, since it uses as much as digits as its factorization.

21247171547 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3035310228.

The product of its digits is 109760, while the sum is 41.

The spelling of 21247171547 in words is "twenty-one billion, two hundred forty-seven million, one hundred seventy-one thousand, five hundred forty-seven".