31425781 has 2 divisors, whose sum is σ = 31425782. Its totient is φ = 31425780.

The previous prime is 31425773. The next prime is 31425787. The reversal of 31425781 is 18752413.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28836900 + 2588881 = 5370^2 + 1609^2 .

It is an emirp because it is prime and its reverse (18752413) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31425781 - 2³ = 31425773 is a prime.

It is a super-2 number, since 2×31425781² = 1975159422919922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31425787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15712890 + 15712891.

It is an arithmetic number, because the mean of its divisors is an integer number (15712891).

Almost surely, 2^31425781 is an apocalyptic number.

It is an amenable number.

31425781 is a deficient number, since it is larger than the sum of its proper divisors (1).

31425781 is an equidigital number, since it uses as much as digits as its factorization.

31425781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6720, while the sum is 31.

The square root of 31425781 is about 5605.8702268247. The cubic root of 31425781 is about 315.5697457241.

The spelling of 31425781 in words is "thirty-one million, four hundred twenty-five thousand, seven hundred eighty-one".