18621978461 has 2 divisors, whose sum is σ = 18621978462. Its totient is φ = 18621978460.

The previous prime is 18621978409. The next prime is 18621978467. The reversal of 18621978461 is 16487912681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15854587225 + 2767391236 = 125915^2 + 52606^2 .

It is a cyclic number.

It is not a de Polignac number, because 18621978461 - 2¹⁸ = 18621716317 is a prime.

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 (18621978467) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9310989230 + 9310989231.

It is an arithmetic number, because the mean of its divisors is an integer number (9310989231).

Almost surely, 2^18621978461 is an apocalyptic number.

It is an amenable number.

18621978461 is a deficient number, since it is larger than the sum of its proper divisors (1).

18621978461 is an equidigital number, since it uses as much as digits as its factorization.

18621978461 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1161216, while the sum is 53.

The spelling of 18621978461 in words is "eighteen billion, six hundred twenty-one million, nine hundred seventy-eight thousand, four hundred sixty-one".