61387981 has 2 divisors, whose sum is σ = 61387982. Its totient is φ = 61387980.

The previous prime is 61387957. The next prime is 61387987. The reversal of 61387981 is 18978316.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 43112356 + 18275625 = 6566^2 + 4275^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61387981 is a prime.

It is a super-2 number, since 2×61387981² = 7536968422512722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61387987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30693990 + 30693991.

It is an arithmetic number, because the mean of its divisors is an integer number (30693991).

Almost surely, 2^61387981 is an apocalyptic number.

It is an amenable number.

61387981 is a deficient number, since it is larger than the sum of its proper divisors (1).

61387981 is an equidigital number, since it uses as much as digits as its factorization.

61387981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 43.

The square root of 61387981 is about 7835.0482449057. The cubic root of 61387981 is about 394.4825377010.

The spelling of 61387981 in words is "sixty-one million, three hundred eighty-seven thousand, nine hundred eighty-one".