21321870 has 32 divisors (see below), whose sum is σ = 51795072. Its totient is φ = 5616672.

The previous prime is 21321869. The next prime is 21321887. The reversal of 21321870 is 7812312.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21321870.

It is a congruent number.

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, 1792 + ... + 6771.

It is an arithmetic number, because the mean of its divisors is an integer number (1618596).

Almost surely, 2^21321870 is an apocalyptic number.

21321870 is an abundant number, since it is smaller than the sum of its proper divisors (30473202).

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

21321870 is a wasteful number, since it uses less digits than its factorization.

21321870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8656.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21321870 is about 4617.5610445342. The cubic root of 21321870 is about 277.2948243935.

The spelling of 21321870 in words is "twenty-one million, three hundred twenty-one thousand, eight hundred seventy".