781978157 has 2 divisors, whose sum is σ = 781978158. Its totient is φ = 781978156.

The previous prime is 781978133. The next prime is 781978187. The reversal of 781978157 is 751879187.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 723287236 + 58690921 = 26894^2 + 7661^2 .

It is a cyclic number.

It is not a de Polignac number, because 781978157 - 2¹⁴ = 781961773 is a prime.

It is a super-2 number, since 2×781978157² = 1222979676050233298, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 781978099 and 781978108.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (781978187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390989078 + 390989079.

It is an arithmetic number, because the mean of its divisors is an integer number (390989079).

Almost surely, 2^781978157 is an apocalyptic number.

It is an amenable number.

781978157 is a deficient number, since it is larger than the sum of its proper divisors (1).

781978157 is an equidigital number, since it uses as much as digits as its factorization.

781978157 is an evil number, because the sum of its binary digits is even.

The product of its digits is 987840, while the sum is 53.

The square root of 781978157 is about 27963.8723534492. The cubic root of 781978157 is about 921.2939248296.

The spelling of 781978157 in words is "seven hundred eighty-one million, nine hundred seventy-eight thousand, one hundred fifty-seven".