21040581 has 8 divisors (see below), whose sum is σ = 29530720. Its totient is φ = 13288752.

The previous prime is 21040559. The next prime is 21040601. The reversal of 21040581 is 18504012.

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

It is not a de Polignac number, because 21040581 - 2⁵ = 21040549 is a prime.

It is a super-2 number, since 2×21040581² = 885412097635122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040511) 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, 184510 + ... + 184623.

It is an arithmetic number, because the mean of its divisors is an integer number (3691340).

Almost surely, 2^21040581 is an apocalyptic number.

It is an amenable number.

21040581 is a deficient number, since it is larger than the sum of its proper divisors (8490139).

21040581 is a wasteful number, since it uses less digits than its factorization.

21040581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 369155.

The product of its (nonzero) digits is 320, while the sum is 21.

The square root of 21040581 is about 4587.0013080443. The cubic root of 21040581 is about 276.0700174177.

Adding to 21040581 its reverse (18504012), we get a palindrome (39544593).

The spelling of 21040581 in words is "twenty-one million, forty thousand, five hundred eighty-one".