21007913 has 2 divisors, whose sum is σ = 21007914. Its totient is φ = 21007912.

The previous prime is 21007891. The next prime is 21007963. The reversal of 21007913 is 31970012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17197609 + 3810304 = 4147^2 + 1952^2 .

It is a cyclic number.

It is not a de Polignac number, because 21007913 - 2⁶ = 21007849 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21007963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503956 + 10503957.

It is an arithmetic number, because the mean of its divisors is an integer number (10503957).

Almost surely, 2^21007913 is an apocalyptic number.

It is an amenable number.

21007913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21007913 is an equidigital number, since it uses as much as digits as its factorization.

21007913 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 378, while the sum is 23.

The square root of 21007913 is about 4583.4389927215. The cubic root of 21007913 is about 275.9270662500.

Adding to 21007913 its reverse (31970012), we get a palindrome (52977925).

The spelling of 21007913 in words is "twenty-one million, seven thousand, nine hundred thirteen".