651621 has 4 divisors (see below), whose sum is σ = 868832. Its totient is φ = 434412.

The previous prime is 651617. The next prime is 651641. The reversal of 651621 is 126156.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 651621 - 2² = 651617 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (651641) 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, 108601 + ... + 108606.

It is an arithmetic number, because the mean of its divisors is an integer number (217208).

2⁶⁵¹⁶²¹ is an apocalyptic number.

It is an amenable number.

651621 is a deficient number, since it is larger than the sum of its proper divisors (217211).

651621 is a wasteful number, since it uses less digits than its factorization.

651621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217210.

The product of its digits is 360, while the sum is 21.

The square root of 651621 is about 807.2304503672. The cubic root of 651621 is about 86.6958596592.

Adding to 651621 its reverse (126156), we get a palindrome (777777).

The spelling of 651621 in words is "six hundred fifty-one thousand, six hundred twenty-one".