21601913 has 2 divisors, whose sum is σ = 21601914. Its totient is φ = 21601912.

The previous prime is 21601903. The next prime is 21601919. The reversal of 21601913 is 31910612.

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., 15904144 + 5697769 = 3988^2 + 2387^2 .

It is a cyclic number.

It is not a de Polignac number, because 21601913 - 2¹⁰ = 21600889 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21601919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10800956 + 10800957.

It is an arithmetic number, because the mean of its divisors is an integer number (10800957).

Almost surely, 2^21601913 is an apocalyptic number.

It is an amenable number.

21601913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21601913 is an equidigital number, since it uses as much as digits as its factorization.

21601913 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 21601913 is about 4647.7858169240. The cubic root of 21601913 is about 278.5035514032.

The spelling of 21601913 in words is "twenty-one million, six hundred one thousand, nine hundred thirteen".