21781696 has 14 divisors (see below), whose sum is σ = 43223180. Its totient is φ = 10890816.

The previous prime is 21781687. The next prime is 21781703. The reversal of 21781696 is 69618712.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 170106 + ... + 170233.

It is an arithmetic number, because the mean of its divisors is an integer number (3087370).

Almost surely, 2^21781696 is an apocalyptic number.

It is an amenable number.

21781696 is a deficient number, since it is larger than the sum of its proper divisors (21441484).

21781696 is an equidigital number, since it uses as much as digits as its factorization.

21781696 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 340351 (or 340341 counting only the distinct ones).

The product of its digits is 36288, while the sum is 40.

The square root of 21781696 is about 4667.0864573093. The cubic root of 21781696 is about 279.2740377756.

The spelling of 21781696 in words is "twenty-one million, seven hundred eighty-one thousand, six hundred ninety-six".