21506275178 has 4 divisors (see below), whose sum is σ = 32259412770. Its totient is φ = 10753137588.

The previous prime is 21506275159. The next prime is 21506275223. The reversal of 21506275178 is 87157260512.

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., 15068299009 + 6437976169 = 122753^2 + 80237^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5376568793 + ... + 5376568796.

Almost surely, 2^21506275178 is an apocalyptic number.

21506275178 is a deficient number, since it is larger than the sum of its proper divisors (10753137592).

21506275178 is a wasteful number, since it uses less digits than its factorization.

21506275178 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10753137591.

The product of its (nonzero) digits is 235200, while the sum is 44.

The spelling of 21506275178 in words is "twenty-one billion, five hundred six million, two hundred seventy-five thousand, one hundred seventy-eight".