21559577978 has 8 divisors (see below), whose sum is σ = 32340780468. Its totient is φ = 10779317824.

The previous prime is 21559577971. The next prime is 21559577993. The reversal of 21559577978 is 87977595512.

It can be written as a sum of positive squares in 2 ways, for example, as 21027030049 + 532547929 = 145007^2 + 23077^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21559577971) 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, 175301 + ... + 271752.

Almost surely, 2^21559577978 is an apocalyptic number.

21559577978 is a deficient number, since it is larger than the sum of its proper divisors (10781202490).

21559577978 is a wasteful number, since it uses less digits than its factorization.

21559577978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 471168.

The product of its digits is 55566000, while the sum is 65.

The spelling of 21559577978 in words is "twenty-one billion, five hundred fifty-nine million, five hundred seventy-seven thousand, nine hundred seventy-eight".