21520106 has 4 divisors (see below), whose sum is σ = 32280162. Its totient is φ = 10760052.

The previous prime is 21520091. The next prime is 21520133. The reversal of 21520106 is 60102512.

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., 12187081 + 9333025 = 3491^2 + 3055^2 .

It is a super-2 number, since 2×21520106² = 926229924502472, which contains 22 as substring.

It is a zygodrome in base 3.

It is an unprimeable number.

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, 5380025 + ... + 5380028.

Almost surely, 2^21520106 is an apocalyptic number.

21520106 is a deficient number, since it is larger than the sum of its proper divisors (10760056).

21520106 is a wasteful number, since it uses less digits than its factorization.

21520106 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10760055.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21520106 is about 4638.9768268445. The cubic root of 21520106 is about 278.1515399662.

Adding to 21520106 its reverse (60102512), we get a palindrome (81622618).

The spelling of 21520106 in words is "twenty-one million, five hundred twenty thousand, one hundred six".