21545541361 has 4 divisors (see below), whose sum is σ = 21545852224. Its totient is φ = 21545230500.

The previous prime is 21545541323. The next prime is 21545541377. The reversal of 21545541361 is 16314554512.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21545541361 - 2⁷ = 21545541233 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21545541361.

It is not an unprimeable number, because it can be changed into a prime (21545541301) 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, 1036 + ... + 207586.

It is an arithmetic number, because the mean of its divisors is an integer number (5386463056).

Almost surely, 2^21545541361 is an apocalyptic number.

It is an amenable number.

21545541361 is a deficient number, since it is larger than the sum of its proper divisors (310863).

21545541361 is a wasteful number, since it uses less digits than its factorization.

21545541361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310862.

The product of its digits is 72000, while the sum is 37.

The spelling of 21545541361 in words is "twenty-one billion, five hundred forty-five million, five hundred forty-one thousand, three hundred sixty-one".