21706147 has 4 divisors (see below), whose sum is σ = 21796456. Its totient is φ = 21615840.

The previous prime is 21706133. The next prime is 21706177. The reversal of 21706147 is 74160712.

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 21706147 - 2⁷ = 21706019 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21706177) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 44793 + ... + 45274.

It is an arithmetic number, because the mean of its divisors is an integer number (5449114).

Almost surely, 2^21706147 is an apocalyptic number.

21706147 is a deficient number, since it is larger than the sum of its proper divisors (90309).

21706147 is an equidigital number, since it uses as much as digits as its factorization.

21706147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90308.

The product of its (nonzero) digits is 2352, while the sum is 28.

The square root of 21706147 is about 4658.9856192094. The cubic root of 21706147 is about 278.9507798906.

Adding to 21706147 its reverse (74160712), we get a palindrome (95866859).

The spelling of 21706147 in words is "twenty-one million, seven hundred six thousand, one hundred forty-seven".