21520186 has 4 divisors (see below), whose sum is σ = 32280282. Its totient is φ = 10760092.

The previous prime is 21520159. The next prime is 21520189. The reversal of 21520186 is 68102512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 13505625 + 8014561 = 3675^2 + 2831^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21520186.

It is not an unprimeable number, because it can be changed into a prime (21520189) 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 as a sum of consecutive naturals, namely, 5380045 + ... + 5380048.

Almost surely, 2^21520186 is an apocalyptic number.

21520186 is a deficient number, since it is larger than the sum of its proper divisors (10760096).

21520186 is a wasteful number, since it uses less digits than its factorization.

21520186 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10760095.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21520186 is about 4638.9854494275. The cubic root of 21520186 is about 278.1518846376.

Adding to 21520186 its reverse (68102512), we get a palindrome (89622698).

The spelling of 21520186 in words is "twenty-one million, five hundred twenty thousand, one hundred eighty-six".