21154663493 has 2 divisors, whose sum is σ = 21154663494. Its totient is φ = 21154663492.

The previous prime is 21154663489. The next prime is 21154663573. The reversal of 21154663493 is 39436645112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13076608609 + 8078054884 = 114353^2 + 89878^2 .

It is a cyclic number.

It is not a de Polignac number, because 21154663493 - 2² = 21154663489 is a prime.

It is a super-2 number, since 2×21154663493² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21154663423) 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, 10577331746 + 10577331747.

It is an arithmetic number, because the mean of its divisors is an integer number (10577331747).

Almost surely, 2^21154663493 is an apocalyptic number.

It is an amenable number.

21154663493 is a deficient number, since it is larger than the sum of its proper divisors (1).

21154663493 is an equidigital number, since it uses as much as digits as its factorization.

21154663493 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 466560, while the sum is 44.

The spelling of 21154663493 in words is "twenty-one billion, one hundred fifty-four million, six hundred sixty-three thousand, four hundred ninety-three".