21131797 has 2 divisors, whose sum is σ = 21131798. Its totient is φ = 21131796.

The previous prime is 21131771. The next prime is 21131813. The reversal of 21131797 is 79713112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20875761 + 256036 = 4569^2 + 506^2 .

It is a cyclic number.

It is not a de Polignac number, because 21131797 - 2¹¹ = 21129749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21131707) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565898 + 10565899.

It is an arithmetic number, because the mean of its divisors is an integer number (10565899).

Almost surely, 2^21131797 is an apocalyptic number.

It is an amenable number.

21131797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131797 is an equidigital number, since it uses as much as digits as its factorization.

21131797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2646, while the sum is 31.

The square root of 21131797 is about 4596.9334343669. The cubic root of 21131797 is about 276.4683856960.

The spelling of 21131797 in words is "twenty-one million, one hundred thirty-one thousand, seven hundred ninety-seven".