31402781 has 2 divisors, whose sum is σ = 31402782. Its totient is φ = 31402780.

The previous prime is 31402769. The next prime is 31402817. The reversal of 31402781 is 18720413.

Together with next prime (31402817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 26429881 + 4972900 = 5141^2 + 2230^2 .

It is a cyclic number.

It is not a de Polignac number, because 31402781 - 2⁶ = 31402717 is a prime.

It is a super-2 number, since 2×31402781² = 1972269309067922, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31402781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31402081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15701390 + 15701391.

It is an arithmetic number, because the mean of its divisors is an integer number (15701391).

Almost surely, 2^31402781 is an apocalyptic number.

It is an amenable number.

31402781 is a deficient number, since it is larger than the sum of its proper divisors (1).

31402781 is an equidigital number, since it uses as much as digits as its factorization.

31402781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 31402781 is about 5603.8184303205. The cubic root of 31402781 is about 315.4927402068.

The spelling of 31402781 in words is "thirty-one million, four hundred two thousand, seven hundred eighty-one".