31661484781 has 2 divisors, whose sum is σ = 31661484782. Its totient is φ = 31661484780.

The previous prime is 31661484761. The next prime is 31661484787. The reversal of 31661484781 is 18748416613.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 29188014025 + 2473470756 = 170845^2 + 49734^2 .

It is a cyclic number.

It is not a de Polignac number, because 31661484781 - 2¹⁹ = 31660960493 is a prime.

It is a super-2 number, since 2×31661484781² (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 (31661484787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15830742390 + 15830742391.

It is an arithmetic number, because the mean of its divisors is an integer number (15830742391).

Almost surely, 2^31661484781 is an apocalyptic number.

It is an amenable number.

31661484781 is a deficient number, since it is larger than the sum of its proper divisors (1).

31661484781 is an equidigital number, since it uses as much as digits as its factorization.

31661484781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 774144, while the sum is 49.

The spelling of 31661484781 in words is "thirty-one billion, six hundred sixty-one million, four hundred eighty-four thousand, seven hundred eighty-one".