21256166 has 8 divisors (see below), whose sum is σ = 32424840. Its totient is φ = 10447888.

The previous prime is 21256153. The next prime is 21256229. The reversal of 21256166 is 66165212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 89951 + ... + 90186.

It is an arithmetic number, because the mean of its divisors is an integer number (4053105).

Almost surely, 2^21256166 is an apocalyptic number.

21256166 is a deficient number, since it is larger than the sum of its proper divisors (11168674).

21256166 is a wasteful number, since it uses less digits than its factorization.

21256166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180198.

The product of its digits is 4320, while the sum is 29.

The square root of 21256166 is about 4610.4409767396. The cubic root of 21256166 is about 277.0097004688.

It can be divided in two parts, 21256 and 166, that multiplied together give a triangular number (3528496 = T₂₆₅₆).

The spelling of 21256166 in words is "twenty-one million, two hundred fifty-six thousand, one hundred sixty-six".