781478721 has 36 divisors (see below), whose sum is σ = 1229928960. Its totient is φ = 477582480.

The previous prime is 781478707. The next prime is 781478723. The reversal of 781478721 is 127874187.

It is not a de Polignac number, because 781478721 - 2¹⁷ = 781347649 is a prime.

It is a super-2 number, since 2×781478721² = 1221417982751591682, which contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is an alternating number because its digits alternate between odd and even.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (781478723) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 96840 + ... + 104598.

Almost surely, 2^781478721 is an apocalyptic number.

It is an amenable number.

781478721 is a deficient number, since it is larger than the sum of its proper divisors (448450239).

781478721 is a wasteful number, since it uses less digits than its factorization.

781478721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7834 (or 7812 counting only the distinct ones).

The product of its digits is 175616, while the sum is 45.

The square root of 781478721 is about 27954.9409049635. The cubic root of 781478721 is about 921.0977448631.

It can be divided in two parts, 78147 and 8721, that added together give a palindrome (86868).

The spelling of 781478721 in words is "seven hundred eighty-one million, four hundred seventy-eight thousand, seven hundred twenty-one".