21166078 has 4 divisors (see below), whose sum is σ = 31749120. Its totient is φ = 10583038.

The previous prime is 21166051. The next prime is 21166099. The reversal of 21166078 is 87066112.

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

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

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, 5291518 + ... + 5291521.

It is an arithmetic number, because the mean of its divisors is an integer number (7937280).

Almost surely, 2^21166078 is an apocalyptic number.

21166078 is a deficient number, since it is larger than the sum of its proper divisors (10583042).

21166078 is a wasteful number, since it uses less digits than its factorization.

21166078 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10583041.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21166078 is about 4600.6606047393. The cubic root of 21166078 is about 276.6178049548.

The spelling of 21166078 in words is "twenty-one million, one hundred sixty-six thousand, seventy-eight".