21816516 has 24 divisors (see below), whose sum is σ = 51135840. Its totient is φ = 7239232.

The previous prime is 21816499. The next prime is 21816539. The reversal of 21816516 is 61561812.

21816516 = T₃₂₀ + T₃₂₁ + ... + T₅₄₆.

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, 1281 + ... + 6728.

It is an arithmetic number, because the mean of its divisors is an integer number (2130660).

Almost surely, 2^21816516 is an apocalyptic number.

It is an amenable number.

21816516 is an abundant number, since it is smaller than the sum of its proper divisors (29319324).

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

21816516 is a wasteful number, since it uses less digits than its factorization.

21816516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8243 (or 8241 counting only the distinct ones).

The product of its digits is 2880, while the sum is 30.

The square root of 21816516 is about 4670.8153463823. The cubic root of 21816516 is about 279.4227734367.

The spelling of 21816516 in words is "twenty-one million, eight hundred sixteen thousand, five hundred sixteen".