651661 has 4 divisors (see below), whose sum is σ = 690012. Its totient is φ = 613312.

The previous prime is 651649. The next prime is 651667. The reversal of 651661 is 166156.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 476100 + 175561 = 690^2 + 419^2 .

It is a cyclic number.

It is not a de Polignac number, because 651661 - 2¹¹ = 649613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (651667) 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 3 ways as a sum of consecutive naturals, for example, 19150 + ... + 19183.

It is an arithmetic number, because the mean of its divisors is an integer number (172503).

2⁶⁵¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

651661 is a deficient number, since it is larger than the sum of its proper divisors (38351).

651661 is a wasteful number, since it uses less digits than its factorization.

651661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38350.

The product of its digits is 1080, while the sum is 25.

The square root of 651661 is about 807.2552260593. The cubic root of 651661 is about 86.6976335756.

The spelling of 651661 in words is "six hundred fifty-one thousand, six hundred sixty-one".