21166401 has 8 divisors (see below), whose sum is σ = 28324864. Its totient is φ = 14059440.

The previous prime is 21166381. The next prime is 21166441. The reversal of 21166401 is 10466112.

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

It is not a de Polignac number, because 21166401 - 2⁶ = 21166337 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21166441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11905 + ... + 13566.

It is an arithmetic number, because the mean of its divisors is an integer number (3540608).

Almost surely, 2^21166401 is an apocalyptic number.

It is an amenable number.

21166401 is a deficient number, since it is larger than the sum of its proper divisors (7158463).

21166401 is a wasteful number, since it uses less digits than its factorization.

21166401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25751.

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 21166401 is about 4600.6957082598. The cubic root of 21166401 is about 276.6192120348.

The spelling of 21166401 in words is "twenty-one million, one hundred sixty-six thousand, four hundred one".