21535081 has 8 divisors (see below), whose sum is σ = 22593600. Its totient is φ = 20497680.

The previous prime is 21535027. The next prime is 21535091. The reversal of 21535081 is 18053512.

It is a happy number.

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 21535081 - 2¹³ = 21526889 is a prime.

It is a super-2 number, since 2×21535081² = 927519427353122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21535001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3171 + ... + 7288.

It is an arithmetic number, because the mean of its divisors is an integer number (2824200).

Almost surely, 2^21535081 is an apocalyptic number.

21535081 is the 2481-st centered heptagonal number.

It is an amenable number.

21535081 is a deficient number, since it is larger than the sum of its proper divisors (1058519).

21535081 is a wasteful number, since it uses less digits than its factorization.

21535081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10559.

The product of its (nonzero) digits is 1200, while the sum is 25.

The square root of 21535081 is about 4640.5905874145. The cubic root of 21535081 is about 278.2160432656.

Adding to 21535081 its reverse (18053512), we get a palindrome (39588593).

The spelling of 21535081 in words is "twenty-one million, five hundred thirty-five thousand, eighty-one".