21786164 has 6 divisors (see below), whose sum is σ = 38125794. Its totient is φ = 10893080.

The previous prime is 21786133. The next prime is 21786173. The reversal of 21786164 is 46168712.

It can be written as a sum of positive squares in only one way, i.e., 20322064 + 1464100 = 4508^2 + 1210^2 .

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2723267 + ... + 2723274.

It is an arithmetic number, because the mean of its divisors is an integer number (6354299).

Almost surely, 2^21786164 is an apocalyptic number.

It is an amenable number.

21786164 is a deficient number, since it is larger than the sum of its proper divisors (16339630).

21786164 is a wasteful number, since it uses less digits than its factorization.

21786164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5446545 (or 5446543 counting only the distinct ones).

The product of its digits is 16128, while the sum is 35.

The square root of 21786164 is about 4667.5651039916. The cubic root of 21786164 is about 279.2931319590.

The spelling of 21786164 in words is "twenty-one million, seven hundred eighty-six thousand, one hundred sixty-four".