21671766 has 16 divisors (see below), whose sum is σ = 48159600. Its totient is φ = 7223904.

The previous prime is 21671743. The next prime is 21671791. The reversal of 21671766 is 66717612.

It is a self number, because there is not a number n which added to its sum of digits gives 21671766.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 200611 + ... + 200718.

It is an arithmetic number, because the mean of its divisors is an integer number (3009975).

Almost surely, 2^21671766 is an apocalyptic number.

21671766 is an abundant number, since it is smaller than the sum of its proper divisors (26487834).

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

21671766 is a wasteful number, since it uses less digits than its factorization.

21671766 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 401340 (or 401334 counting only the distinct ones).

The product of its digits is 21168, while the sum is 36.

The square root of 21671766 is about 4655.2944052981. The cubic root of 21671766 is about 278.8034226337.

The spelling of 21671766 in words is "twenty-one million, six hundred seventy-one thousand, seven hundred sixty-six".