21821516 has 6 divisors (see below), whose sum is σ = 38187660. Its totient is φ = 10910756.

The previous prime is 21821507. The next prime is 21821533. The reversal of 21821516 is 61512812.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2727686 + ... + 2727693.

It is an arithmetic number, because the mean of its divisors is an integer number (6364610).

Almost surely, 2^21821516 is an apocalyptic number.

It is an amenable number.

21821516 is a deficient number, since it is larger than the sum of its proper divisors (16366144).

21821516 is a wasteful number, since it uses less digits than its factorization.

21821516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5455383 (or 5455381 counting only the distinct ones).

The product of its digits is 960, while the sum is 26.

The square root of 21821516 is about 4671.3505541760. The cubic root of 21821516 is about 279.4441182311. Note that the first 3 decimals are identical.

The spelling of 21821516 in words is "twenty-one million, eight hundred twenty-one thousand, five hundred sixteen".