21172830 has 32 divisors (see below), whose sum is σ = 58074624. Its totient is φ = 4839456.

The previous prime is 21172829. The next prime is 21172849. The reversal of 21172830 is 3827112.

It is a self number, because there is not a number n which added to its sum of digits gives 21172830.

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, 50202 + ... + 50621.

It is an arithmetic number, because the mean of its divisors is an integer number (1814832).

Almost surely, 2^21172830 is an apocalyptic number.

21172830 is an abundant number, since it is smaller than the sum of its proper divisors (36901794).

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

21172830 is a wasteful number, since it uses less digits than its factorization.

21172830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100840.

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

The square root of 21172830 is about 4601.3943538888. The cubic root of 21172830 is about 276.6472156129.

Adding to 21172830 its reverse (3827112), we get a palindrome (24999942).

The spelling of 21172830 in words is "twenty-one million, one hundred seventy-two thousand, eight hundred thirty".