21018071 has 4 divisors (see below), whose sum is σ = 21465312. Its totient is φ = 20570832.

The previous prime is 21018043. The next prime is 21018073. The reversal of 21018071 is 17081012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21018071 is a prime.

It is a super-2 number, since 2×21018071² = 883518617122082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018073) 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 3 ways as a sum of consecutive naturals, for example, 223550 + ... + 223643.

It is an arithmetic number, because the mean of its divisors is an integer number (5366328).

Almost surely, 2^21018071 is an apocalyptic number.

21018071 is a deficient number, since it is larger than the sum of its proper divisors (447241).

21018071 is an equidigital number, since it uses as much as digits as its factorization.

21018071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 447240.

The product of its (nonzero) digits is 112, while the sum is 20.

The square root of 21018071 is about 4584.5469787101. The cubic root of 21018071 is about 275.9715322805.

Adding to 21018071 its reverse (17081012), we get a palindrome (38099083).

It can be divided in two parts, 210 and 18071, that added together give a palindrome (18281).

The spelling of 21018071 in words is "twenty-one million, eighteen thousand, seventy-one".