70387781 has 2 divisors, whose sum is σ = 70387782. Its totient is φ = 70387780.

The previous prime is 70387747. The next prime is 70387783. The reversal of 70387781 is 18778307.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54626881 + 15760900 = 7391^2 + 3970^2 .

It is an emirp because it is prime and its reverse (18778307) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 70387781 - 2²⁶ = 3278917 is a prime.

It is a super-2 number, since 2×70387781² = 9908879428207922, which contains 22 as substring.

Together with 70387783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (70387783) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35193890 + 35193891.

It is an arithmetic number, because the mean of its divisors is an integer number (35193891).

Almost surely, 2^70387781 is an apocalyptic number.

It is an amenable number.

70387781 is a deficient number, since it is larger than the sum of its proper divisors (1).

70387781 is an equidigital number, since it uses as much as digits as its factorization.

70387781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 65856, while the sum is 41.

The square root of 70387781 is about 8389.7426063021. The cubic root of 70387781 is about 412.8881557270. Note that the first 3 decimals are identical.

The spelling of 70387781 in words is "seventy million, three hundred eighty-seven thousand, seven hundred eighty-one".