21011001989 has 2 divisors, whose sum is σ = 21011001990. Its totient is φ = 21011001988.

The previous prime is 21011001953. The next prime is 21011002031. The reversal of 21011001989 is 98910011012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12191913889 + 8819088100 = 110417^2 + 93910^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011001989 is a prime.

It is a super-2 number, since 2×21011001989² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011001919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505500994 + 10505500995.

It is an arithmetic number, because the mean of its divisors is an integer number (10505500995).

Almost surely, 2^21011001989 is an apocalyptic number.

It is an amenable number.

21011001989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011001989 is an equidigital number, since it uses as much as digits as its factorization.

21011001989 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 32.

The spelling of 21011001989 in words is "twenty-one billion, eleven million, one thousand, nine hundred eighty-nine".