21555013313 has 4 divisors (see below), whose sum is σ = 21573709188. Its totient is φ = 21536317440.

The previous prime is 21555013301. The next prime is 21555013321. The reversal of 21555013313 is 31331055512.

It is a happy number.

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 7948257409 + 13606755904 = 89153^2 + 116648^2 .

It is a cyclic number.

It is not a de Polignac number, because 21555013313 - 2⁸ = 21555013057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21555012313) 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, 9346208 + ... + 9348513.

It is an arithmetic number, because the mean of its divisors is an integer number (5393427297).

Almost surely, 2^21555013313 is an apocalyptic number.

It is an amenable number.

21555013313 is a deficient number, since it is larger than the sum of its proper divisors (18695875).

21555013313 is a wasteful number, since it uses less digits than its factorization.

21555013313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18695874.

The product of its (nonzero) digits is 6750, while the sum is 29.

Adding to 21555013313 its reverse (31331055512), we get a palindrome (52886068825).

The spelling of 21555013313 in words is "twenty-one billion, five hundred fifty-five million, thirteen thousand, three hundred thirteen".