21997985 has 8 divisors (see below), whose sum is σ = 26439936. Its totient is φ = 17570160.

The previous prime is 21997981. The next prime is 21998027. The reversal of 21997985 is 58979912.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21997985 - 2² = 21997981 is a prime.

It is a super-2 number, since 2×21997985² = 967822688120450, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21997981) 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, 272 + ... + 6638.

It is an arithmetic number, because the mean of its divisors is an integer number (3304992).

Almost surely, 2^21997985 is an apocalyptic number.

It is an amenable number.

21997985 is a deficient number, since it is larger than the sum of its proper divisors (4441951).

21997985 is an equidigital number, since it uses as much as digits as its factorization.

21997985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7063.

The product of its digits is 408240, while the sum is 50.

The square root of 21997985 is about 4690.2009551831. The cubic root of 21997985 is about 280.1953780934.

The spelling of 21997985 in words is "twenty-one million, nine hundred ninety-seven thousand, nine hundred eighty-five".