1620987817 has 2 divisors, whose sum is σ = 1620987818. Its totient is φ = 1620987816.

The previous prime is 1620987803. The next prime is 1620987829. The reversal of 1620987817 is 7187890261.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1614352041 + 6635776 = 40179^2 + 2576^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1620987817 is a prime.

It is not a weakly prime, because it can be changed into another prime (1620987887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810493908 + 810493909.

It is an arithmetic number, because the mean of its divisors is an integer number (810493909).

Almost surely, 2^1620987817 is an apocalyptic number.

It is an amenable number.

1620987817 is a deficient number, since it is larger than the sum of its proper divisors (1).

1620987817 is an equidigital number, since it uses as much as digits as its factorization.

1620987817 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 338688, while the sum is 49.

The square root of 1620987817 is about 40261.4929802659. The cubic root of 1620987817 is about 1174.6989582182.

The spelling of 1620987817 in words is "one billion, six hundred twenty million, nine hundred eighty-seven thousand, eight hundred seventeen".