21940913 has 2 divisors, whose sum is σ = 21940914. Its totient is φ = 21940912.

The previous prime is 21940909. The next prime is 21940927. The reversal of 21940913 is 31904912.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21003889 + 937024 = 4583^2 + 968^2 .

It is a cyclic number.

It is not a de Polignac number, because 21940913 - 2² = 21940909 is a prime.

It is not a weakly prime, because it can be changed into another prime (21940943) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10970456 + 10970457.

It is an arithmetic number, because the mean of its divisors is an integer number (10970457).

Almost surely, 2^21940913 is an apocalyptic number.

It is an amenable number.

21940913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21940913 is an equidigital number, since it uses as much as digits as its factorization.

21940913 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 21940913 is about 4684.1128295548. The cubic root of 21940913 is about 279.9528534564.

The spelling of 21940913 in words is "twenty-one million, nine hundred forty thousand, nine hundred thirteen".