21873810 has 32 divisors (see below), whose sum is σ = 59997312. Its totient is φ = 4999680.

The previous prime is 21873809. The next prime is 21873821. The reversal of 21873810 is 1837812.

It is a happy number.

It is a super-2 number, since 2×21873810² = 956927127832200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 51871 + ... + 52290.

It is an arithmetic number, because the mean of its divisors is an integer number (1874916).

Almost surely, 2^21873810 is an apocalyptic number.

21873810 is an abundant number, since it is smaller than the sum of its proper divisors (38123502).

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

21873810 is a wasteful number, since it uses less digits than its factorization.

21873810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104178.

The product of its (nonzero) digits is 2688, while the sum is 30.

The square root of 21873810 is about 4676.9445153861. The cubic root of 21873810 is about 279.6671640385.

The spelling of 21873810 in words is "twenty-one million, eight hundred seventy-three thousand, eight hundred ten".