21861204493 has 2 divisors, whose sum is σ = 21861204494. Its totient is φ = 21861204492.

The previous prime is 21861204437. The next prime is 21861204559. The reversal of 21861204493 is 39440216812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11664648009 + 10196556484 = 108003^2 + 100978^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21861204493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21861204403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10930602246 + 10930602247.

It is an arithmetic number, because the mean of its divisors is an integer number (10930602247).

Almost surely, 2^21861204493 is an apocalyptic number.

It is an amenable number.

21861204493 is a deficient number, since it is larger than the sum of its proper divisors (1).

21861204493 is an equidigital number, since it uses as much as digits as its factorization.

21861204493 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 82944, while the sum is 40.

The spelling of 21861204493 in words is "twenty-one billion, eight hundred sixty-one million, two hundred four thousand, four hundred ninety-three".