21011331021 has 4 divisors (see below), whose sum is σ = 28015108032. Its totient is φ = 14007554012.

The previous prime is 21011330987. The next prime is 21011331023. The reversal of 21011331021 is 12013311012.

It is a happy number.

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 not a de Polignac number, because 21011331021 - 2¹¹ = 21011328973 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011331023) 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, 3501888501 + ... + 3501888506.

It is an arithmetic number, because the mean of its divisors is an integer number (7003777008).

Almost surely, 2^21011331021 is an apocalyptic number.

It is an amenable number.

21011331021 is a deficient number, since it is larger than the sum of its proper divisors (7003777011).

21011331021 is an equidigital number, since it uses as much as digits as its factorization.

21011331021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7003777010.

The product of its (nonzero) digits is 36, while the sum is 15.

Adding to 21011331021 its reverse (12013311012), we get a palindrome (33024642033).

The spelling of 21011331021 in words is "twenty-one billion, eleven million, three hundred thirty-one thousand, twenty-one".