616261981 has 2 divisors, whose sum is σ = 616261982. Its totient is φ = 616261980.

The previous prime is 616261967. The next prime is 616261991. The reversal of 616261981 is 189162616.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 436433881 + 179828100 = 20891^2 + 13410^2 .

It is a cyclic number.

It is not a de Polignac number, because 616261981 - 2⁵ = 616261949 is a prime.

It is a super-2 number, since 2×616261981² = 759557658452088722, which contains 22 as substring.

It is equal to p_32128978 and since 616261981 and 32128978 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (616261991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 308130990 + 308130991.

It is an arithmetic number, because the mean of its divisors is an integer number (308130991).

Almost surely, 2^616261981 is an apocalyptic number.

It is an amenable number.

616261981 is a deficient number, since it is larger than the sum of its proper divisors (1).

616261981 is an equidigital number, since it uses as much as digits as its factorization.

616261981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 40.

The square root of 616261981 is about 24824.6244886000. The cubic root of 616261981 is about 850.9847783550.

The spelling of 616261981 in words is "six hundred sixteen million, two hundred sixty-one thousand, nine hundred eighty-one".