21505027 has 4 divisors (see below), whose sum is σ = 21662136. Its totient is φ = 21347920.

The previous prime is 21505019. The next prime is 21505039. The reversal of 21505027 is 72050512.

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

It is a cyclic number.

It is not a de Polignac number, because 21505027 - 2³ = 21505019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21504989 and 21505007.

It is not an unprimeable number, because it can be changed into a prime (21505007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 78349 + ... + 78622.

It is an arithmetic number, because the mean of its divisors is an integer number (5415534).

Almost surely, 2^21505027 is an apocalyptic number.

21505027 is a deficient number, since it is larger than the sum of its proper divisors (157109).

21505027 is a wasteful number, since it uses less digits than its factorization.

21505027 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157108.

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 21505027 is about 4637.3512914163. The cubic root of 21505027 is about 278.0865584542.

Adding to 21505027 its reverse (72050512), we get a palindrome (93555539).

The spelling of 21505027 in words is "twenty-one million, five hundred five thousand, twenty-seven".