21820513 has 16 divisors (see below), whose sum is σ = 25768512. Its totient is φ = 18216000.

The previous prime is 21820489. The next prime is 21820517. The reversal of 21820513 is 31502812.

It is not a de Polignac number, because 21820513 - 2⁵ = 21820481 is a prime.

It is a super-3 number, since 3×21820513³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21820517) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47103 + ... + 47563.

It is an arithmetic number, because the mean of its divisors is an integer number (1610532).

Almost surely, 2^21820513 is an apocalyptic number.

It is an amenable number.

21820513 is a deficient number, since it is larger than the sum of its proper divisors (3947999).

21820513 is a wasteful number, since it uses less digits than its factorization.

21820513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 816.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21820513 is about 4671.2431964093. The cubic root of 21820513 is about 279.4398367268.

The spelling of 21820513 in words is "twenty-one million, eight hundred twenty thousand, five hundred thirteen".