1691624681 has 2 divisors, whose sum is σ = 1691624682. Its totient is φ = 1691624680.

The previous prime is 1691624569. The next prime is 1691624689. The reversal of 1691624681 is 1864261961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1438305625 + 253319056 = 37925^2 + 15916^2 .

It is an emirp because it is prime and its reverse (1864261961) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1691624681 is a prime.

It is a super-2 number, since 2×1691624681² = 5723188122736703522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1691624689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 845812340 + 845812341.

It is an arithmetic number, because the mean of its divisors is an integer number (845812341).

Almost surely, 2^1691624681 is an apocalyptic number.

It is an amenable number.

1691624681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1691624681 is an equidigital number, since it uses as much as digits as its factorization.

1691624681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 44.

The square root of 1691624681 is about 41129.3651908220. The cubic root of 1691624681 is about 1191.5200031368.

The spelling of 1691624681 in words is "one billion, six hundred ninety-one million, six hundred twenty-four thousand, six hundred eighty-one".