618721 has 4 divisors (see below), whose sum is σ = 624832. Its totient is φ = 612612.

The previous prime is 618719. The next prime is 618799. The reversal of 618721 is 127816.

618721 = T₅₄ + T₅₅ + ... + T₁₅₆.

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 a cyclic number.

It is not a de Polignac number, because 618721 - 2¹ = 618719 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (618421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2901 + ... + 3106.

It is an arithmetic number, because the mean of its divisors is an integer number (156208).

2⁶¹⁸⁷²¹ is an apocalyptic number.

It is an amenable number.

618721 is a deficient number, since it is larger than the sum of its proper divisors (6111).

618721 is a wasteful number, since it uses less digits than its factorization.

618721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6110.

The product of its digits is 672, while the sum is 25.

The square root of 618721 is about 786.5882023016. The cubic root of 618721 is about 85.2115147507.

The spelling of 618721 in words is "six hundred eighteen thousand, seven hundred twenty-one".