21147397918 has 4 divisors (see below), whose sum is σ = 31721096880. Its totient is φ = 10573698958.

The previous prime is 21147397897. The next prime is 21147397919. The reversal of 21147397918 is 81979374112.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147397919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5286849478 + ... + 5286849481.

It is an arithmetic number, because the mean of its divisors is an integer number (7930274220).

Almost surely, 2^21147397918 is an apocalyptic number.

21147397918 is a deficient number, since it is larger than the sum of its proper divisors (10573698962).

21147397918 is a wasteful number, since it uses less digits than its factorization.

21147397918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10573698961.

The product of its digits is 762048, while the sum is 52.

The spelling of 21147397918 in words is "twenty-one billion, one hundred forty-seven million, three hundred ninety-seven thousand, nine hundred eighteen".