1620971999 has 2 divisors, whose sum is σ = 1620972000. Its totient is φ = 1620971998.

The previous prime is 1620971969. The next prime is 1620972011. The reversal of 1620971999 is 9991790261.

It is a strong prime.

It is an emirp because it is prime and its reverse (9991790261) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1620971999 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1620971999.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1620971969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810485999 + 810486000.

It is an arithmetic number, because the mean of its divisors is an integer number (810486000).

Almost surely, 2^1620971999 is an apocalyptic number.

1620971999 is a deficient number, since it is larger than the sum of its proper divisors (1).

1620971999 is an equidigital number, since it uses as much as digits as its factorization.

1620971999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 551124, while the sum is 53.

The square root of 1620971999 is about 40261.2965389839. The cubic root of 1620971999 is about 1174.6951372048.

The spelling of 1620971999 in words is "one billion, six hundred twenty million, nine hundred seventy-one thousand, nine hundred ninety-nine".