21704947 has 4 divisors (see below), whose sum is σ = 23678136. Its totient is φ = 19731760.

The previous prime is 21704941. The next prime is 21704957. The reversal of 21704947 is 74940712.

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 21704947 - 2⁷ = 21704819 is a prime.

It is a super-2 number, since 2×21704947² = 942209448545618, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21704941) 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, 986578 + ... + 986599.

It is an arithmetic number, because the mean of its divisors is an integer number (5919534).

Almost surely, 2^21704947 is an apocalyptic number.

21704947 is a deficient number, since it is larger than the sum of its proper divisors (1973189).

21704947 is a wasteful number, since it uses less digits than its factorization.

21704947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1973188.

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 21704947 is about 4658.8568340313. The cubic root of 21704947 is about 278.9456393021.

It can be divided in two parts, 2170 and 4947, that added together give a palindrome (7117).

The spelling of 21704947 in words is "twenty-one million, seven hundred four thousand, nine hundred forty-seven".