1917921891623 has 2 divisors, whose sum is σ = 1917921891624. Its totient is φ = 1917921891622.

The previous prime is 1917921891439. The next prime is 1917921891667. The reversal of 1917921891623 is 3261981297191.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1917921891623 - 2³⁸ = 1643043984679 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1917921899623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 958960945811 + 958960945812.

It is an arithmetic number, because the mean of its divisors is an integer number (958960945812).

Almost surely, 2^{1917921891623} is an apocalyptic number.

1917921891623 is a deficient number, since it is larger than the sum of its proper divisors (1).

1917921891623 is an equidigital number, since it uses as much as digits as its factorization.

1917921891623 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2939328, while the sum is 59.

The spelling of 1917921891623 in words is "one trillion, nine hundred seventeen billion, nine hundred twenty-one million, eight hundred ninety-one thousand, six hundred twenty-three".