31820477581 has 2 divisors, whose sum is σ = 31820477582. Its totient is φ = 31820477580.

The previous prime is 31820477543. The next prime is 31820477593. The reversal of 31820477581 is 18577402813.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27173874025 + 4646603556 = 164845^2 + 68166^2 .

It is a cyclic number.

It is not a de Polignac number, because 31820477581 - 2⁷ = 31820477453 is a prime.

It is a super-2 number, since 2×31820477581² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31820477281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15910238790 + 15910238791.

It is an arithmetic number, because the mean of its divisors is an integer number (15910238791).

Almost surely, 2^31820477581 is an apocalyptic number.

It is an amenable number.

31820477581 is a deficient number, since it is larger than the sum of its proper divisors (1).

31820477581 is an equidigital number, since it uses as much as digits as its factorization.

31820477581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 376320, while the sum is 46.

The spelling of 31820477581 in words is "thirty-one billion, eight hundred twenty million, four hundred seventy-seven thousand, five hundred eighty-one".