20981585 has 8 divisors (see below), whose sum is σ = 25438056. Its totient is φ = 16611840.

The previous prime is 20981581. The next prime is 20981593. The reversal of 20981585 is 58518902.

It can be written as a sum of positive squares in 4 ways, for example, as 2076481 + 18905104 = 1441^2 + 4348^2 .

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

It is not a de Polignac number, because 20981585 - 2² = 20981581 is a prime.

It is a super-2 number, since 2×20981585² = 880453818224450, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20981581) 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, 21146 + ... + 22115.

It is an arithmetic number, because the mean of its divisors is an integer number (3179757).

Almost surely, 2^20981585 is an apocalyptic number.

It is an amenable number.

20981585 is a deficient number, since it is larger than the sum of its proper divisors (4456471).

20981585 is an equidigital number, since it uses as much as digits as its factorization.

20981585 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43363.

The product of its (nonzero) digits is 28800, while the sum is 38.

The square root of 20981585 is about 4580.5660130600. The cubic root of 20981585 is about 275.8117502627.

The spelling of 20981585 in words is "twenty million, nine hundred eighty-one thousand, five hundred eighty-five".