21947618897 has 4 divisors (see below), whose sum is σ = 21967163760. Its totient is φ = 21928074036.

The previous prime is 21947618887. The next prime is 21947618899. The reversal of 21947618897 is 79881674912.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21947618897 - 2¹⁴ = 21947602513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21947618899) 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, 9770747 + ... + 9772992.

It is an arithmetic number, because the mean of its divisors is an integer number (5491790940).

Almost surely, 2^21947618897 is an apocalyptic number.

It is an amenable number.

21947618897 is a deficient number, since it is larger than the sum of its proper divisors (19544863).

21947618897 is a wasteful number, since it uses less digits than its factorization.

21947618897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19544862.

The product of its digits is 12192768, while the sum is 62.

The spelling of 21947618897 in words is "twenty-one billion, nine hundred forty-seven million, six hundred eighteen thousand, eight hundred ninety-seven".