21106513 has 4 divisors (see below), whose sum is σ = 21621348. Its totient is φ = 20591680.

The previous prime is 21106471. The next prime is 21106523. The reversal of 21106513 is 31560112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3069504 + 18037009 = 1752^2 + 4247^2 .

It is a cyclic number.

It is not a de Polignac number, because 21106513 - 2¹⁷ = 20975441 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21106523) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 257356 + ... + 257437.

It is an arithmetic number, because the mean of its divisors is an integer number (5405337).

Almost surely, 2^21106513 is an apocalyptic number.

It is an amenable number.

21106513 is a deficient number, since it is larger than the sum of its proper divisors (514835).

21106513 is an equidigital number, since it uses as much as digits as its factorization.

21106513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 514834.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 21106513 is about 4594.1825170535. The cubic root of 21106513 is about 276.3580777332.

Adding to 21106513 its reverse (31560112), we get a palindrome (52666625).

The spelling of 21106513 in words is "twenty-one million, one hundred six thousand, five hundred thirteen".