781247921 has 2 divisors, whose sum is σ = 781247922. Its totient is φ = 781247920.

The previous prime is 781247917. The next prime is 781247953. The reversal of 781247921 is 129742187.

781247921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 539911696 + 241336225 = 23236^2 + 15535^2 .

It is a cyclic number.

It is not a de Polignac number, because 781247921 - 2² = 781247917 is a prime.

It is a super-2 number, since 2×781247921² = 1220696628133644482, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (781240921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390623960 + 390623961.

It is an arithmetic number, because the mean of its divisors is an integer number (390623961).

Almost surely, 2^781247921 is an apocalyptic number.

It is an amenable number.

781247921 is a deficient number, since it is larger than the sum of its proper divisors (1).

781247921 is an equidigital number, since it uses as much as digits as its factorization.

781247921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 56448, while the sum is 41.

The square root of 781247921 is about 27950.8125284400. The cubic root of 781247921 is about 921.0070576885.

The spelling of 781247921 in words is "seven hundred eighty-one million, two hundred forty-seven thousand, nine hundred twenty-one".