21953647 has 4 divisors (see below), whose sum is σ = 23245056. Its totient is φ = 20662240.

The previous prime is 21953641. The next prime is 21953677. The reversal of 21953647 is 74635912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21953647 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21953641) 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 3 ways as a sum of consecutive naturals, for example, 645679 + ... + 645712.

It is an arithmetic number, because the mean of its divisors is an integer number (5811264).

Almost surely, 2^21953647 is an apocalyptic number.

21953647 is a deficient number, since it is larger than the sum of its proper divisors (1291409).

21953647 is a wasteful number, since it uses less digits than its factorization.

21953647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1291408.

The product of its digits is 45360, while the sum is 37.

The square root of 21953647 is about 4685.4719079299. The cubic root of 21953647 is about 280.0070023759.

The spelling of 21953647 in words is "twenty-one million, nine hundred fifty-three thousand, six hundred forty-seven".