31421999981 has 2 divisors, whose sum is σ = 31421999982. Its totient is φ = 31421999980.

The previous prime is 31421999927. The next prime is 31422000007. The reversal of 31421999981 is 18999912413.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 22707777481 + 8714222500 = 150691^2 + 93350^2 .

It is a cyclic number.

It is not a de Polignac number, because 31421999981 - 2¹⁴ = 31421983597 is a prime.

It is a super-2 number, since 2×31421999981² (a number of 22 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31421999381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15710999990 + 15710999991.

It is an arithmetic number, because the mean of its divisors is an integer number (15710999991).

Almost surely, 2^31421999981 is an apocalyptic number.

It is an amenable number.

31421999981 is a deficient number, since it is larger than the sum of its proper divisors (1).

31421999981 is an equidigital number, since it uses as much as digits as its factorization.

31421999981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1259712, while the sum is 56.

The spelling of 31421999981 in words is "thirty-one billion, four hundred twenty-one million, nine hundred ninety-nine thousand, nine hundred eighty-one".