21000913 has 2 divisors, whose sum is σ = 21000914. Its totient is φ = 21000912.

The previous prime is 21000911. The next prime is 21000953. The reversal of 21000913 is 31900012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20948929 + 51984 = 4577^2 + 228^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000913 - 2¹ = 21000911 is a prime.

Together with 21000911, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21000911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500456 + 10500457.

It is an arithmetic number, because the mean of its divisors is an integer number (10500457).

Almost surely, 2^21000913 is an apocalyptic number.

It is an amenable number.

21000913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000913 is an equidigital number, since it uses as much as digits as its factorization.

21000913 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 54, while the sum is 16.

The square root of 21000913 is about 4582.6753103400. The cubic root of 21000913 is about 275.8964158306.

Adding to 21000913 its reverse (31900012), we get a palindrome (52900925).

The spelling of 21000913 in words is "twenty-one million, nine hundred thirteen", and thus it is an aban number.