21811870 has 32 divisors (see below), whose sum is σ = 40678848. Its totient is φ = 8414208.

The previous prime is 21811861. The next prime is 21811873. The reversal of 21811870 is 7811812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21811873) 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 15 ways as a sum of consecutive naturals, for example, 61614 + ... + 61966.

It is an arithmetic number, because the mean of its divisors is an integer number (1271214).

Almost surely, 2^21811870 is an apocalyptic number.

21811870 is a deficient number, since it is larger than the sum of its proper divisors (18866978).

21811870 is a wasteful number, since it uses less digits than its factorization.

21811870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 564.

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 21811870 is about 4670.3179763267. The cubic root of 21811870 is about 279.4029369304.

The spelling of 21811870 in words is "twenty-one million, eight hundred eleven thousand, eight hundred seventy".