21947905 has 8 divisors (see below), whose sum is σ = 30100032. Its totient is φ = 15049968.

The previous prime is 21947903. The next prime is 21947921. The reversal of 21947905 is 50974912.

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

It is a cyclic number.

It is not a de Polignac number, because 21947905 - 2¹ = 21947903 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21947903) 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 7 ways as a sum of consecutive naturals, for example, 313507 + ... + 313576.

It is an arithmetic number, because the mean of its divisors is an integer number (3762504).

Almost surely, 2^21947905 is an apocalyptic number.

It is an amenable number.

21947905 is a deficient number, since it is larger than the sum of its proper divisors (8152127).

21947905 is an equidigital number, since it uses as much as digits as its factorization.

21947905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 627095.

The product of its (nonzero) digits is 22680, while the sum is 37.

The square root of 21947905 is about 4684.8591227485. The cubic root of 21947905 is about 279.9825882030.

The spelling of 21947905 in words is "twenty-one million, nine hundred forty-seven thousand, nine hundred five".