21997750 has 16 divisors (see below), whose sum is σ = 41180256. Its totient is φ = 8799000.

The previous prime is 21997733. The next prime is 21997751. The reversal of 21997750 is 5779912.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 43746 + ... + 44245.

It is an arithmetic number, because the mean of its divisors is an integer number (2573766).

Almost surely, 2^21997750 is an apocalyptic number.

21997750 is a deficient number, since it is larger than the sum of its proper divisors (19182506).

21997750 is an equidigital number, since it uses as much as digits as its factorization.

21997750 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88008 (or 87998 counting only the distinct ones).

The product of its (nonzero) digits is 39690, while the sum is 40.

The square root of 21997750 is about 4690.1759028847. The cubic root of 21997750 is about 280.1943803331.

It can be divided in two parts, 219 and 97750, that added together give a square (97969 = 313²).

The spelling of 21997750 in words is "twenty-one million, nine hundred ninety-seven thousand, seven hundred fifty".