21553740178 has 4 divisors (see below), whose sum is σ = 32330610270. Its totient is φ = 10776870088.

The previous prime is 21553740167. The next prime is 21553740193. The reversal of 21553740178 is 87104735512.

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., 20989345129 + 564395049 = 144877^2 + 23757^2 .

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 5388435043 + ... + 5388435046.

Almost surely, 2^21553740178 is an apocalyptic number.

21553740178 is a deficient number, since it is larger than the sum of its proper divisors (10776870092).

21553740178 is a wasteful number, since it uses less digits than its factorization.

21553740178 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10776870091.

The product of its (nonzero) digits is 235200, while the sum is 43.

The spelling of 21553740178 in words is "twenty-one billion, five hundred fifty-three million, seven hundred forty thousand, one hundred seventy-eight".