21706866 has 20 divisors (see below), whose sum is σ = 48639822. Its totient is φ = 7235568.

The previous prime is 21706837. The next prime is 21706889. The reversal of 21706866 is 66860712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 19053225 + 2653641 = 4365^2 + 1629^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21706866.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 66835 + ... + 67158.

Almost surely, 2^21706866 is an apocalyptic number.

21706866 is an abundant number, since it is smaller than the sum of its proper divisors (26932956).

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

21706866 is a wasteful number, since it uses less digits than its factorization.

21706866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134007 (or 133998 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 21706866 is about 4659.0627812898. The cubic root of 21706866 is about 278.9538598690.

The spelling of 21706866 in words is "twenty-one million, seven hundred six thousand, eight hundred sixty-six".