21995 has 8 divisors (see below), whose sum is σ = 27216. Its totient is φ = 17056.

The previous prime is 21991. The next prime is 21997. The reversal of 21995 is 59912.

It is a happy number.

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 21995 - 2² = 21991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21991) 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, 224 + ... + 306.

It is an arithmetic number, because the mean of its divisors is an integer number (3402).

2²¹⁹⁹⁵ is an apocalyptic number.

21995 is a deficient number, since it is larger than the sum of its proper divisors (5221).

21995 is an equidigital number, since it uses as much as digits as its factorization.

21995 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141.

The product of its digits is 810, while the sum is 26.

The square root of 21995 is about 148.3071137876. The cubic root of 21995 is about 28.0182703886.

The spelling of 21995 in words is "twenty-one thousand, nine hundred ninety-five".