661947 has 16 divisors (see below), whose sum is σ = 1037568. Its totient is φ = 370080.

The previous prime is 661939. The next prime is 661949. The reversal of 661947 is 749166.

It is a happy number.

It is not a de Polignac number, because 661947 - 2³ = 661939 is a prime.

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

661947 is a lucky number.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (661949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 343 + ... + 1200.

It is an arithmetic number, because the mean of its divisors is an integer number (64848).

2⁶⁶¹⁹⁴⁷ is an apocalyptic number.

661947 is a deficient number, since it is larger than the sum of its proper divisors (375621).

661947 is a wasteful number, since it uses less digits than its factorization.

661947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1570.

The product of its digits is 9072, while the sum is 33.

The square root of 661947 is about 813.6012536863. The cubic root of 661947 is about 87.1514076405.

It can be divided in two parts, 6619 and 47, that added together give a palindrome (6666).

The spelling of 661947 in words is "six hundred sixty-one thousand, nine hundred forty-seven".