21240947 has 8 divisors (see below), whose sum is σ = 26142816. Its totient is φ = 16805952.

The previous prime is 21240913. The next prime is 21240971. The reversal of 21240947 is 74904212.

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 21240947 - 2¹⁰ = 21239923 is a prime.

It is a super-3 number, since 3×21240947³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21240907) 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, 116618 + ... + 116799.

It is an arithmetic number, because the mean of its divisors is an integer number (3267852).

Almost surely, 2^21240947 is an apocalyptic number.

21240947 is a deficient number, since it is larger than the sum of its proper divisors (4901869).

21240947 is a wasteful number, since it uses less digits than its factorization.

21240947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 233437.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21240947 is about 4608.7901883249. The cubic root of 21240947 is about 276.9435735047.

The spelling of 21240947 in words is "twenty-one million, two hundred forty thousand, nine hundred forty-seven".