21012223021 has 2 divisors, whose sum is σ = 21012223022. Its totient is φ = 21012223020.

The previous prime is 21012222991. The next prime is 21012223031. The reversal of 21012223021 is 12032221012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11709620521 + 9302602500 = 108211^2 + 96450^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012223021 - 2⁷ = 21012222893 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21012222986 and 21012223004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21012223031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506111510 + 10506111511.

It is an arithmetic number, because the mean of its divisors is an integer number (10506111511).

Almost surely, 2^21012223021 is an apocalyptic number.

It is an amenable number.

21012223021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012223021 is an equidigital number, since it uses as much as digits as its factorization.

21012223021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 16.

Adding to 21012223021 its reverse (12032221012), we get a palindrome (33044444033).

The spelling of 21012223021 in words is "twenty-one billion, twelve million, two hundred twenty-three thousand, twenty-one".