21597018 has 16 divisors (see below), whose sum is σ = 44587776. Its totient is φ = 6966720.

The previous prime is 21597001. The next prime is 21597019. The reversal of 21597018 is 81079512.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21597018.

It is not an unprimeable number, because it can be changed into a prime (21597019) 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, 57871 + ... + 58242.

It is an arithmetic number, because the mean of its divisors is an integer number (2786736).

Almost surely, 2^21597018 is an apocalyptic number.

21597018 is an abundant number, since it is smaller than the sum of its proper divisors (22990758).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21597018 is a wasteful number, since it uses less digits than its factorization.

21597018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116149.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21597018 is about 4647.2591922552. The cubic root of 21597018 is about 278.4825134844.

The spelling of 21597018 in words is "twenty-one million, five hundred ninety-seven thousand, eighteen".