21516784 has 10 divisors (see below), whose sum is σ = 41688800. Its totient is φ = 10758384.

The previous prime is 21516767. The next prime is 21516791. The reversal of 21516784 is 48761512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 672384 + ... + 672415.

It is an arithmetic number, because the mean of its divisors is an integer number (4168880).

Almost surely, 2^21516784 is an apocalyptic number.

It is an amenable number.

21516784 is a deficient number, since it is larger than the sum of its proper divisors (20172016).

21516784 is a wasteful number, since it uses less digits than its factorization.

21516784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1344807 (or 1344801 counting only the distinct ones).

The product of its digits is 13440, while the sum is 34.

The square root of 21516784 is about 4638.6187599327. The cubic root of 21516784 is about 278.1372267318.

The spelling of 21516784 in words is "twenty-one million, five hundred sixteen thousand, seven hundred eighty-four".