21084581 has 8 divisors (see below), whose sum is σ = 24281664. Its totient is φ = 17933760.

The previous prime is 21084559. The next prime is 21084587. The reversal of 21084581 is 18548012.

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 21084581 - 2¹⁸ = 20822437 is a prime.

It is a super-2 number, since 2×21084581² = 889119111891122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21084587) 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, 10580 + ... + 12413.

It is an arithmetic number, because the mean of its divisors is an integer number (3035208).

Almost surely, 2^21084581 is an apocalyptic number.

It is an amenable number.

21084581 is a deficient number, since it is larger than the sum of its proper divisors (3197083).

21084581 is a wasteful number, since it uses less digits than its factorization.

21084581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23131.

The product of its (nonzero) digits is 2560, while the sum is 29.

The square root of 21084581 is about 4591.7949649347. The cubic root of 21084581 is about 276.2623223621.

The spelling of 21084581 in words is "twenty-one million, eighty-four thousand, five hundred eighty-one".