18621978491 has 2 divisors, whose sum is σ = 18621978492. Its totient is φ = 18621978490.

The previous prime is 18621978469. The next prime is 18621978547. The reversal of 18621978491 is 19487912681.

It is an a-pointer prime, because the next prime (18621978547) can be obtained adding 18621978491 to its sum of digits (56).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 18621978491 - 2³⁴ = 1442109307 is a prime.

It is not a weakly prime, because it can be changed into another prime (18621978461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9310989245 + 9310989246.

It is an arithmetic number, because the mean of its divisors is an integer number (9310989246).

Almost surely, 2^18621978491 is an apocalyptic number.

18621978491 is a deficient number, since it is larger than the sum of its proper divisors (1).

18621978491 is an equidigital number, since it uses as much as digits as its factorization.

18621978491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1741824, while the sum is 56.

The spelling of 18621978491 in words is "eighteen billion, six hundred twenty-one million, nine hundred seventy-eight thousand, four hundred ninety-one".