71977981 has 2 divisors, whose sum is σ = 71977982. Its totient is φ = 71977980.

The previous prime is 71977973. The next prime is 71978003. The reversal of 71977981 is 18977917.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55502500 + 16475481 = 7450^2 + 4059^2 .

It is a cyclic number.

It is not a de Polignac number, because 71977981 - 2³ = 71977973 is a prime.

It is a super-2 number, since 2×71977981² = 10361659497672722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71977901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35988990 + 35988991.

It is an arithmetic number, because the mean of its divisors is an integer number (35988991).

Almost surely, 2^71977981 is an apocalyptic number.

It is an amenable number.

71977981 is a deficient number, since it is larger than the sum of its proper divisors (1).

71977981 is an equidigital number, since it uses as much as digits as its factorization.

71977981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 222264, while the sum is 49.

The square root of 71977981 is about 8483.9837930067. The cubic root of 71977981 is about 415.9743516146.

Subtracting from 71977981 its product of digits (222264), we obtain a palindrome (71755717).

The spelling of 71977981 in words is "seventy-one million, nine hundred seventy-seven thousand, nine hundred eighty-one".