21087776 has 24 divisors (see below), whose sum is σ = 42531804. Its totient is φ = 10286080.

The previous prime is 21087763. The next prime is 21087779. The reversal of 21087776 is 67778012.

It can be written as a sum of positive squares in 2 ways, for example, as 17007376 + 4080400 = 4124^2 + 2020^2 .

It is not an unprimeable number, because it can be changed into a prime (21087779) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6725 + ... + 9348.

Almost surely, 2^21087776 is an apocalyptic number.

It is an amenable number.

21087776 is an abundant number, since it is smaller than the sum of its proper divisors (21444028).

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

21087776 is a wasteful number, since it uses less digits than its factorization.

21087776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16124 (or 16116 counting only the distinct ones).

The product of its (nonzero) digits is 32928, while the sum is 38.

The square root of 21087776 is about 4592.1428549208. The cubic root of 21087776 is about 276.2762759006.

The spelling of 21087776 in words is "twenty-one million, eighty-seven thousand, seven hundred seventy-six".