21131211001 has 4 divisors (see below), whose sum is σ = 21140991604. Its totient is φ = 21121430400.

The previous prime is 21131210983. The next prime is 21131211047. The reversal of 21131211001 is 10011213112.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7469107776 + 13662103225 = 86424^2 + 116885^2 .

It is a cyclic number.

It is not a de Polignac number, because 21131211001 - 2¹⁷ = 21131079929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131211071) 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, 4887060 + ... + 4891381.

It is an arithmetic number, because the mean of its divisors is an integer number (5285247901).

Almost surely, 2^21131211001 is an apocalyptic number.

It is an amenable number.

21131211001 is a deficient number, since it is larger than the sum of its proper divisors (9780603).

21131211001 is an equidigital number, since it uses as much as digits as its factorization.

21131211001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9780602.

The product of its (nonzero) digits is 12, while the sum is 13.

Adding to 21131211001 its reverse (10011213112), we get a palindrome (31142424113).

The spelling of 21131211001 in words is "twenty-one billion, one hundred thirty-one million, two hundred eleven thousand, one".