17621978842421 has 2 divisors, whose sum is σ = 17621978842422. Its totient is φ = 17621978842420.

The previous prime is 17621978842309. The next prime is 17621978842453. The reversal of 17621978842421 is 12424887912671.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9792956596900 + 7829022245521 = 3129370^2 + 2798039^2 .

It is a cyclic number.

It is not a de Polignac number, because 17621978842421 - 2²⁶ = 17621911733557 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 (17621978841421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8810989421210 + 8810989421211.

It is an arithmetic number, because the mean of its divisors is an integer number (8810989421211).

Almost surely, 2^{17621978842421} is an apocalyptic number.

It is an amenable number.

17621978842421 is a deficient number, since it is larger than the sum of its proper divisors (1).

17621978842421 is an equidigital number, since it uses as much as digits as its factorization.

17621978842421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21676032, while the sum is 62.

The spelling of 17621978842421 in words is "seventeen trillion, six hundred twenty-one billion, nine hundred seventy-eight million, eight hundred forty-two thousand, four hundred twenty-one".