21531213111 has 4 divisors (see below), whose sum is σ = 28708284152. Its totient is φ = 14354142072.

The previous prime is 21531213107. The next prime is 21531213113. The reversal of 21531213111 is 11131213512.

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

It is not a de Polignac number, because 21531213111 - 2² = 21531213107 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531213113) 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, 3588535516 + ... + 3588535521.

It is an arithmetic number, because the mean of its divisors is an integer number (7177071038).

Almost surely, 2^21531213111 is an apocalyptic number.

21531213111 is a deficient number, since it is larger than the sum of its proper divisors (7177071041).

21531213111 is an equidigital number, since it uses as much as digits as its factorization.

21531213111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7177071040.

The product of its digits is 180, while the sum is 21.

Adding to 21531213111 its reverse (11131213512), we get a palindrome (32662426623).

The spelling of 21531213111 in words is "twenty-one billion, five hundred thirty-one million, two hundred thirteen thousand, one hundred eleven".