21981147 has 8 divisors (see below), whose sum is σ = 29331456. Its totient is φ = 14642472.

The previous prime is 21981143. The next prime is 21981149. The reversal of 21981147 is 74118912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21981147 - 2² = 21981143 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21981143) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 3558 + ... + 7524.

It is an arithmetic number, because the mean of its divisors is an integer number (3666432).

Almost surely, 2^21981147 is an apocalyptic number.

21981147 is a deficient number, since it is larger than the sum of its proper divisors (7350309).

21981147 is a wasteful number, since it uses less digits than its factorization.

21981147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5817.

The product of its digits is 4032, while the sum is 33.

The square root of 21981147 is about 4688.4055925229. The cubic root of 21981147 is about 280.1238695129.

The spelling of 21981147 in words is "twenty-one million, nine hundred eighty-one thousand, one hundred forty-seven".