21487716 has 36 divisors (see below), whose sum is σ = 54463500. Its totient is φ = 7143168.

The previous prime is 21487709. The next prime is 21487717. The reversal of 21487716 is 61778412.

It can be written as a sum of positive squares in 2 ways, for example, as 11902500 + 9585216 = 3450^2 + 3096^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21487717) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 19960 + ... + 21008.

It is an arithmetic number, because the mean of its divisors is an integer number (1512875).

Almost surely, 2^21487716 is an apocalyptic number.

It is an amenable number.

21487716 is an abundant number, since it is smaller than the sum of its proper divisors (32975784).

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

21487716 is a wasteful number, since it uses less digits than its factorization.

21487716 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1628 (or 1623 counting only the distinct ones).

The product of its digits is 18816, while the sum is 36.

The square root of 21487716 is about 4635.4844407030. The cubic root of 21487716 is about 278.0119208869.

The spelling of 21487716 in words is "twenty-one million, four hundred eighty-seven thousand, seven hundred sixteen".