21555368159018 has 4 divisors (see below), whose sum is σ = 32333052238530. Its totient is φ = 10777684079508.

The previous prime is 21555368158967. The next prime is 21555368159041. The reversal of 21555368159018 is 81095186355512.

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

It can be written as a sum of positive squares in only one way, i.e., 14206242959689 + 7349125199329 = 3769117^2 + 2710927^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5388842039753 + ... + 5388842039756.

Almost surely, 2^{21555368159018} is an apocalyptic number.

21555368159018 is a deficient number, since it is larger than the sum of its proper divisors (10777684079512).

21555368159018 is a wasteful number, since it uses less digits than its factorization.

21555368159018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10777684079511.

The product of its (nonzero) digits is 12960000, while the sum is 59.

The spelling of 21555368159018 in words is "twenty-one trillion, five hundred fifty-five billion, three hundred sixty-eight million, one hundred fifty-nine thousand, eighteen".