651631 has 4 divisors (see below), whose sum is σ = 653752. Its totient is φ = 649512.

The previous prime is 651617. The next prime is 651641. The reversal of 651631 is 136156.

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

It is a cyclic number.

It is not a de Polignac number, because 651631 - 2⁷ = 651503 is a prime.

It is a super-2 number, since 2×651631² = 849245920322, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

651631 is a lucky 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 (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 501 + ... + 1246.

It is an arithmetic number, because the mean of its divisors is an integer number (163438).

2⁶⁵¹⁶³¹ is an apocalyptic number.

651631 is a deficient number, since it is larger than the sum of its proper divisors (2121).

651631 is a wasteful number, since it uses less digits than its factorization.

651631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2120.

The product of its digits is 540, while the sum is 22.

The square root of 651631 is about 807.2366443615. The cubic root of 651631 is about 86.6963031451.

Adding to 651631 its reverse (136156), we get a palindrome (787787).

The spelling of 651631 in words is "six hundred fifty-one thousand, six hundred thirty-one".