781221 has 8 divisors (see below), whose sum is σ = 1190464. Its totient is φ = 446400.

The previous prime is 781217. The next prime is 781229. The reversal of 781221 is 122187.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 781221 - 2² = 781217 is a prime.

It is a super-2 number, since 2×781221² = 1220612501682, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 37201 = 781221 / (7 + 8 + 1 + 2 + 2 + 1).

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (781229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18580 + ... + 18621.

It is an arithmetic number, because the mean of its divisors is an integer number (148808).

2⁷⁸¹²²¹ is an apocalyptic number.

It is an amenable number.

781221 is a deficient number, since it is larger than the sum of its proper divisors (409243).

781221 is a wasteful number, since it uses less digits than its factorization.

781221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37211.

The product of its digits is 224, while the sum is 21.

The square root of 781221 is about 883.8670714536. The cubic root of 781221 is about 92.0996478582.

The spelling of 781221 in words is "seven hundred eighty-one thousand, two hundred twenty-one".