205213550021 has 4 divisors (see below), whose sum is σ = 216014263200. Its totient is φ = 194412836844.

The previous prime is 205213549999. The next prime is 205213550023. The reversal of 205213550021 is 120055312502.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205213550021 is a prime.

It is a super-2 number, since 2×205213550021² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205213550023) 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, 5400356561 + ... + 5400356598.

It is an arithmetic number, because the mean of its divisors is an integer number (54003565800).

Almost surely, 2^205213550021 is an apocalyptic number.

It is an amenable number.

205213550021 is a deficient number, since it is larger than the sum of its proper divisors (10800713179).

205213550021 is a wasteful number, since it uses less digits than its factorization.

205213550021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10800713178.

The product of its (nonzero) digits is 3000, while the sum is 26.

Adding to 205213550021 its reverse (120055312502), we get a palindrome (325268862523).

The spelling of 205213550021 in words is "two hundred five billion, two hundred thirteen million, five hundred fifty thousand, twenty-one".