17978143921 has 4 divisors (see below), whose sum is σ = 17979361344. Its totient is φ = 17976926500.

The previous prime is 17978143891. The next prime is 17978143927. The reversal of 17978143921 is 12934187971.

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 17978143921 - 2⁵ = 17978143889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (17978143927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 586285 + ... + 616186.

It is an arithmetic number, because the mean of its divisors is an integer number (4494840336).

Almost surely, 2^17978143921 is an apocalyptic number.

It is an amenable number.

17978143921 is a deficient number, since it is larger than the sum of its proper divisors (1217423).

17978143921 is a wasteful number, since it uses less digits than its factorization.

17978143921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1217422.

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

The spelling of 17978143921 in words is "seventeen billion, nine hundred seventy-eight million, one hundred forty-three thousand, nine hundred twenty-one".