21993571 has 8 divisors (see below), whose sum is σ = 22834080. Its totient is φ = 21158592.

The previous prime is 21993541. The next prime is 21993581. The reversal of 21993571 is 17539912.

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 21993571 - 2¹⁷ = 21862499 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21993571.

It is not an unprimeable number, because it can be changed into a prime (21993541) 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 7 ways as a sum of consecutive naturals, for example, 7866 + ... + 10288.

It is an arithmetic number, because the mean of its divisors is an integer number (2854260).

Almost surely, 2^21993571 is an apocalyptic number.

21993571 is a deficient number, since it is larger than the sum of its proper divisors (840509).

21993571 is a wasteful number, since it uses less digits than its factorization.

21993571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2765.

The product of its digits is 17010, while the sum is 37.

The square root of 21993571 is about 4689.7303760451. The cubic root of 21993571 is about 280.1766359960.

The spelling of 21993571 in words is "twenty-one million, nine hundred ninety-three thousand, five hundred seventy-one".