21531205411 has 4 divisors (see below), whose sum is σ = 22273660800. Its totient is φ = 20788750024.

The previous prime is 21531205393. The next prime is 21531205417. The reversal of 21531205411 is 11450213512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21531205411 - 2¹⁷ = 21531074339 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21531205417) 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, 371227651 + ... + 371227708.

It is an arithmetic number, because the mean of its divisors is an integer number (5568415200).

Almost surely, 2^21531205411 is an apocalyptic number.

21531205411 is a deficient number, since it is larger than the sum of its proper divisors (742455389).

21531205411 is an equidigital number, since it uses as much as digits as its factorization.

21531205411 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 742455388.

The product of its (nonzero) digits is 1200, while the sum is 25.

Adding to 21531205411 its reverse (11450213512), we get a palindrome (32981418923).

The spelling of 21531205411 in words is "twenty-one billion, five hundred thirty-one million, two hundred five thousand, four hundred eleven".