21890805 has 32 divisors (see below), whose sum is σ = 36495360. Its totient is φ = 11192640.

The previous prime is 21890801. The next prime is 21890807. The reversal of 21890805 is 50809812.

21890805 = 448² + 449² + ... + 537².

It is a happy number.

It is not a de Polignac number, because 21890805 - 2² = 21890801 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21890801) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 83104 + ... + 83366.

It is an arithmetic number, because the mean of its divisors is an integer number (1140480).

Almost surely, 2^21890805 is an apocalyptic number.

It is an amenable number.

21890805 is a deficient number, since it is larger than the sum of its proper divisors (14604555).

21890805 is a wasteful number, since it uses less digits than its factorization.

21890805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 481.

The product of its (nonzero) digits is 5760, while the sum is 33.

The square root of 21890805 is about 4678.7610539543. The cubic root of 21890805 is about 279.7395750335.

The spelling of 21890805 in words is "twenty-one million, eight hundred ninety thousand, eight hundred five".