21157224 has 32 divisors (see below), whose sum is σ = 57702240. Its totient is φ = 6411200.

The previous prime is 21157207. The next prime is 21157243. The reversal of 21157224 is 42275112.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a junction number, because it is equal to n+sod(n) for n = 21157194 and 21157203.

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 7 ways as a sum of consecutive naturals, for example, 39807 + ... + 40334.

It is an arithmetic number, because the mean of its divisors is an integer number (1803195).

Almost surely, 2^21157224 is an apocalyptic number.

21157224 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21157224 is an abundant number, since it is smaller than the sum of its proper divisors (36545016).

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

21157224 is a wasteful number, since it uses less digits than its factorization.

21157224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80161 (or 80157 counting only the distinct ones).

The product of its digits is 1120, while the sum is 24.

The square root of 21157224 is about 4599.6982509726. The cubic root of 21157224 is about 276.5792288326.

It can be divided in two parts, 2115 and 7224, that added together give a palindrome (9339).

The spelling of 21157224 in words is "twenty-one million, one hundred fifty-seven thousand, two hundred twenty-four".