61931981 has 2 divisors, whose sum is σ = 61931982. Its totient is φ = 61931980.

The previous prime is 61931927. The next prime is 61931983. The reversal of 61931981 is 18913916.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61763881 + 168100 = 7859^2 + 410^2 .

It is a cyclic number.

It is not a de Polignac number, because 61931981 - 2¹⁸ = 61669837 is a prime.

It is a super-3 number, since 3×61931981³ (a number of 24 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

Together with 61931983, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_3669815 and since 61931981 and 3669815 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 (61931983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30965990 + 30965991.

It is an arithmetic number, because the mean of its divisors is an integer number (30965991).

Almost surely, 2^61931981 is an apocalyptic number.

It is an amenable number.

61931981 is a deficient number, since it is larger than the sum of its proper divisors (1).

61931981 is an equidigital number, since it uses as much as digits as its factorization.

61931981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11664, while the sum is 38.

The square root of 61931981 is about 7869.6874779117. The cubic root of 61931981 is about 395.6443704635.

The spelling of 61931981 in words is "sixty-one million, nine hundred thirty-one thousand, nine hundred eighty-one".