21905797 has 2 divisors, whose sum is σ = 21905798. Its totient is φ = 21905796.

The previous prime is 21905783. The next prime is 21905827. The reversal of 21905797 is 79750912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21215236 + 690561 = 4606^2 + 831^2 .

It is a cyclic number.

It is not a de Polignac number, because 21905797 - 2¹⁵ = 21873029 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21905297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10952898 + 10952899.

It is an arithmetic number, because the mean of its divisors is an integer number (10952899).

Almost surely, 2^21905797 is an apocalyptic number.

It is an amenable number.

21905797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21905797 is an equidigital number, since it uses as much as digits as its factorization.

21905797 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 39690, while the sum is 40.

The square root of 21905797 is about 4680.3629132793. The cubic root of 21905797 is about 279.8034206935.

The spelling of 21905797 in words is "twenty-one million, nine hundred five thousand, seven hundred ninety-seven".