21997755 has 48 divisors (see below), whose sum is σ = 42422016. Its totient is φ = 10471680.

The previous prime is 21997753. The next prime is 21997777. The reversal of 21997755 is 55779912.

It is not a de Polignac number, because 21997755 - 2¹ = 21997753 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21997755.

It is not an unprimeable number, because it can be changed into a prime (21997751) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 17529 + ... + 18741.

It is an arithmetic number, because the mean of its divisors is an integer number (883792).

Almost surely, 2^21997755 is an apocalyptic number.

21997755 is a deficient number, since it is larger than the sum of its proper divisors (20424261).

21997755 is a wasteful number, since it uses less digits than its factorization.

21997755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1268 (or 1265 counting only the distinct ones).

The product of its digits is 198450, while the sum is 45.

The square root of 21997755 is about 4690.1764359137. The cubic root of 21997755 is about 280.1944015621.

The spelling of 21997755 in words is "twenty-one million, nine hundred ninety-seven thousand, seven hundred fifty-five".