781855961 has 2 divisors, whose sum is σ = 781855962. Its totient is φ = 781855960.

The previous prime is 781855939. The next prime is 781855973. The reversal of 781855961 is 169558187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 773118025 + 8737936 = 27805^2 + 2956^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-781855961 is a prime.

It is a super-2 number, since 2×781855961² = 1222597487502467042, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (781855661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390927980 + 390927981.

It is an arithmetic number, because the mean of its divisors is an integer number (390927981).

Almost surely, 2^781855961 is an apocalyptic number.

It is an amenable number.

781855961 is a deficient number, since it is larger than the sum of its proper divisors (1).

781855961 is an equidigital number, since it uses as much as digits as its factorization.

781855961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 604800, while the sum is 50.

The square root of 781855961 is about 27961.6873775529. The cubic root of 781855961 is about 921.2459335926.

The spelling of 781855961 in words is "seven hundred eighty-one million, eight hundred fifty-five thousand, nine hundred sixty-one".