21213945553 has 4 divisors (see below), whose sum is σ = 21707293168. Its totient is φ = 20720597940.

The previous prime is 21213945547. The next prime is 21213945559. The reversal of 21213945553 is 35554931212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (21213945547) and next prime (21213945559).

It is a cyclic number.

It is not a de Polignac number, because 21213945553 - 2²⁵ = 21180391121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21213945559) 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, 246673743 + ... + 246673828.

It is an arithmetic number, because the mean of its divisors is an integer number (5426823292).

Almost surely, 2^21213945553 is an apocalyptic number.

It is an amenable number.

21213945553 is a deficient number, since it is larger than the sum of its proper divisors (493347615).

21213945553 is an equidigital number, since it uses as much as digits as its factorization.

21213945553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 493347614.

The product of its digits is 162000, while the sum is 40.

The spelling of 21213945553 in words is "twenty-one billion, two hundred thirteen million, nine hundred forty-five thousand, five hundred fifty-three".