21000329621 has 2 divisors, whose sum is σ = 21000329622. Its totient is φ = 21000329620.

The previous prime is 21000329617. The next prime is 21000329629. The reversal of 21000329621 is 12692300012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13481532100 + 7518797521 = 116110^2 + 86711^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000329621 - 2² = 21000329617 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000329629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500164810 + 10500164811.

It is an arithmetic number, because the mean of its divisors is an integer number (10500164811).

Almost surely, 2^21000329621 is an apocalyptic number.

It is an amenable number.

21000329621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000329621 is an equidigital number, since it uses as much as digits as its factorization.

21000329621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 26.

Adding to 21000329621 its reverse (12692300012), we get a palindrome (33692629633).

The spelling of 21000329621 in words is "twenty-one billion, three hundred twenty-nine thousand, six hundred twenty-one".