780738021 has 30 divisors (see below), whose sum is σ = 1356708870. Its totient is φ = 446133744.

The previous prime is 780738017. The next prime is 780738037. The reversal of 780738021 is 120837087.

It can be written as a sum of positive squares in only one way, i.e., 411521796 + 369216225 = 20286^2 + 19215^2 .

It is not a de Polignac number, because 780738021 - 2² = 780738017 is a prime.

It is a super-5 number, since 5×780738021⁵ (a number of 46 digits) contains 55555 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (780738011) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 94386 + ... + 102323.

It is an arithmetic number, because the mean of its divisors is an integer number (45223629).

Almost surely, 2^780738021 is an apocalyptic number.

It is an amenable number.

780738021 is a deficient number, since it is larger than the sum of its proper divisors (575970849).

780738021 is a wasteful number, since it uses less digits than its factorization.

780738021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196735 (or 196719 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The square root of 780738021 is about 27941.6896590024. The cubic root of 780738021 is about 920.8066417075.

The spelling of 780738021 in words is "seven hundred eighty million, seven hundred thirty-eight thousand, twenty-one".