21018516 has 24 divisors (see below), whose sum is σ = 50369760. Its totient is φ = 6816672.

The previous prime is 21018509. The next prime is 21018523. The reversal of 21018516 is 61581012.

It is an interprime number because it is at equal distance from previous prime (21018509) and next prime (21018523).

It is a plaindrome in base 13.

It is a congruent number.

It is an unprimeable number.

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, 23226 + ... + 24113.

It is an arithmetic number, because the mean of its divisors is an integer number (2098740).

Almost surely, 2^21018516 is an apocalyptic number.

It is an amenable number.

21018516 is an abundant number, since it is smaller than the sum of its proper divisors (29351244).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21018516 is a wasteful number, since it uses less digits than its factorization.

21018516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47383 (or 47381 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 21018516 is about 4584.5955110566. The cubic root of 21018516 is about 275.9734799135.

Adding to 21018516 its reverse (61581012), we get a palindrome (82599528).

The spelling of 21018516 in words is "twenty-one million, eighteen thousand, five hundred sixteen".