21403866 has 16 divisors (see below), whose sum is σ = 46699488. Its totient is φ = 6486000.

The previous prime is 21403849. The next prime is 21403883. The reversal of 21403866 is 66830412.

It is an interprime number because it is at equal distance from previous prime (21403849) and next prime (21403883).

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, 162085 + ... + 162216.

It is an arithmetic number, because the mean of its divisors is an integer number (2918718).

Almost surely, 2^21403866 is an apocalyptic number.

21403866 is an abundant number, since it is smaller than the sum of its proper divisors (25295622).

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

21403866 is a wasteful number, since it uses less digits than its factorization.

21403866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324317.

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 21403866 is about 4626.4312380062. The cubic root of 21403866 is about 277.6498273775.

It can be divided in two parts, 2140 and 3866, that added together give a palindrome (6006).

The spelling of 21403866 in words is "twenty-one million, four hundred three thousand, eight hundred sixty-six".