681945 has 16 divisors (see below), whose sum is σ = 1190592. Its totient is φ = 330560.

The previous prime is 681943. The next prime is 681949. The reversal of 681945 is 549186.

It is not a de Polignac number, because 681945 - 2¹ = 681943 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a Curzon number.

681945 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (681943) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1902 + ... + 2231.

It is an arithmetic number, because the mean of its divisors is an integer number (74412).

2⁶⁸¹⁹⁴⁵ is an apocalyptic number.

It is an amenable number.

681945 is a deficient number, since it is larger than the sum of its proper divisors (508647).

681945 is a wasteful number, since it uses less digits than its factorization.

681945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4152.

The product of its digits is 8640, while the sum is 33.

The square root of 681945 is about 825.7996124969. The cubic root of 681945 is about 88.0203551398.

It can be divided in two parts, 681 and 945, that multiplied together give a triangular number (643545 = T₁₁₃₄).

The spelling of 681945 in words is "six hundred eighty-one thousand, nine hundred forty-five".