21178147 has 4 divisors (see below), whose sum is σ = 22098960. Its totient is φ = 20257336.

The previous prime is 21178133. The next prime is 21178151. The reversal of 21178147 is 74187112.

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

It is a cyclic number.

It is not a de Polignac number, because 21178147 - 2⁷ = 21178019 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21178187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 460372 + ... + 460417.

It is an arithmetic number, because the mean of its divisors is an integer number (5524740).

Almost surely, 2^21178147 is an apocalyptic number.

21178147 is a deficient number, since it is larger than the sum of its proper divisors (920813).

21178147 is an equidigital number, since it uses as much as digits as its factorization.

21178147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 920812.

The product of its digits is 3136, while the sum is 31.

The square root of 21178147 is about 4601.9720772730. The cubic root of 21178147 is about 276.6703712347.

The spelling of 21178147 in words is "twenty-one million, one hundred seventy-eight thousand, one hundred forty-seven".