21687234 has 16 divisors (see below), whose sum is σ = 43986240. Its totient is φ = 7127120.

The previous prime is 21687233. The next prime is 21687251. The reversal of 21687234 is 43278612.

It is a super-2 number, since 2×21687234² = 940672237141512, which contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21687195 and 21687204.

It is not an unprimeable number, because it can be changed into a prime (21687233) 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 7 ways as a sum of consecutive naturals, for example, 25029 + ... + 25880.

It is an arithmetic number, because the mean of its divisors is an integer number (2749140).

Almost surely, 2^21687234 is an apocalyptic number.

21687234 is an abundant number, since it is smaller than the sum of its proper divisors (22299006).

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

21687234 is a wasteful number, since it uses less digits than its factorization.

21687234 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50985.

The product of its digits is 16128, while the sum is 33.

The square root of 21687234 is about 4656.9554432054. The cubic root of 21687234 is about 278.8697378837.

The spelling of 21687234 in words is "twenty-one million, six hundred eighty-seven thousand, two hundred thirty-four".