21975647 has 4 divisors (see below), whose sum is σ = 23132280. Its totient is φ = 20819016.

The previous prime is 21975637. The next prime is 21975691. The reversal of 21975647 is 74657912.

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 21975647 - 2¹⁴ = 21959263 is a prime.

It is a super-2 number, since 2×21975647² = 965858122137218, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21975637) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 578288 + ... + 578325.

It is an arithmetic number, because the mean of its divisors is an integer number (5783070).

Almost surely, 2^21975647 is an apocalyptic number.

21975647 is a deficient number, since it is larger than the sum of its proper divisors (1156633).

21975647 is a wasteful number, since it uses less digits than its factorization.

21975647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1156632.

The product of its digits is 105840, while the sum is 41.

The square root of 21975647 is about 4687.8190024787. The cubic root of 21975647 is about 280.1005038866.

It can be divided in two parts, 21975 and 647, that added together give a palindrome (22622).

The spelling of 21975647 in words is "twenty-one million, nine hundred seventy-five thousand, six hundred forty-seven".