21452581 has 8 divisors (see below), whose sum is σ = 21690144. Its totient is φ = 21216720.

The previous prime is 21452569. The next prime is 21452591. The reversal of 21452581 is 18525412.

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 21452581 - 2⁵ = 21452549 is a prime.

It is a super-2 number, since 2×21452581² = 920426463123122, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21452591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61650 + ... + 61996.

It is an arithmetic number, because the mean of its divisors is an integer number (2711268).

Almost surely, 2^21452581 is an apocalyptic number.

It is an amenable number.

21452581 is a deficient number, since it is larger than the sum of its proper divisors (237563).

21452581 is a wasteful number, since it uses less digits than its factorization.

21452581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 851.

The product of its digits is 3200, while the sum is 28.

The square root of 21452581 is about 4631.6931029592. The cubic root of 21452581 is about 277.8603105808.

Adding to 21452581 its reverse (18525412), we get a palindrome (39977993).

The spelling of 21452581 in words is "twenty-one million, four hundred fifty-two thousand, five hundred eighty-one".