21158643797 has 2 divisors, whose sum is σ = 21158643798. Its totient is φ = 21158643796.

The previous prime is 21158643787. The next prime is 21158643871. The reversal of 21158643797 is 79734685112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20645666596 + 512977201 = 143686^2 + 22649^2 .

It is a cyclic number.

It is not a de Polignac number, because 21158643797 - 2¹⁰ = 21158642773 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21158643787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10579321898 + 10579321899.

It is an arithmetic number, because the mean of its divisors is an integer number (10579321899).

Almost surely, 2^21158643797 is an apocalyptic number.

It is an amenable number.

21158643797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21158643797 is an equidigital number, since it uses as much as digits as its factorization.

21158643797 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2540160, while the sum is 53.

The spelling of 21158643797 in words is "twenty-one billion, one hundred fifty-eight million, six hundred forty-three thousand, seven hundred ninety-seven".