21815830 has 16 divisors (see below), whose sum is σ = 40623120. Its totient is φ = 8425312.

The previous prime is 21815797. The next prime is 21815837. The reversal of 21815830 is 3851812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21815837) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 37324 + ... + 37903.

It is an arithmetic number, because the mean of its divisors is an integer number (2538945).

Almost surely, 2^21815830 is an apocalyptic number.

21815830 is a deficient number, since it is larger than the sum of its proper divisors (18807290).

21815830 is a wasteful number, since it uses less digits than its factorization.

21815830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75263.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 21815830 is about 4670.7419110886. The cubic root of 21815830 is about 279.4198446765.

The spelling of 21815830 in words is "twenty-one million, eight hundred fifteen thousand, eight hundred thirty".