21532081 has 4 divisors (see below), whose sum is σ = 22798692. Its totient is φ = 20265472.

The previous prime is 21532067. The next prime is 21532087. The reversal of 21532081 is 18023512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11451456 + 10080625 = 3384^2 + 3175^2 .

It is a cyclic number.

It is not a de Polignac number, because 21532081 - 2⁷ = 21531953 is a prime.

It is a super-2 number, since 2×21532081² = 927261024381122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21532087) 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 3 ways as a sum of consecutive naturals, for example, 633280 + ... + 633313.

It is an arithmetic number, because the mean of its divisors is an integer number (5699673).

Almost surely, 2^21532081 is an apocalyptic number.

It is an amenable number.

21532081 is a deficient number, since it is larger than the sum of its proper divisors (1266611).

21532081 is a wasteful number, since it uses less digits than its factorization.

21532081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1266610.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21532081 is about 4640.2673414363. The cubic root of 21532081 is about 278.2031234645.

Adding to 21532081 its reverse (18023512), we get a palindrome (39555593).

The spelling of 21532081 in words is "twenty-one million, five hundred thirty-two thousand, eighty-one".