623921 has 4 divisors (see below), whose sum is σ = 651072. Its totient is φ = 596772.

The previous prime is 623893. The next prime is 623923. The reversal of 623921 is 129326.

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, and also an emirpimes, since its reverse is a distinct semiprime: 129326 = 2 ⋅64663.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-623921 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 27127 = 623921 / (6 + 2 + 3 + 9 + 2 + 1).

It is a Duffinian number.

It is a nialpdrome in base 16.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 623921.

It is not an unprimeable number, because it can be changed into a prime (623923) 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, 13541 + ... + 13586.

It is an arithmetic number, because the mean of its divisors is an integer number (162768).

2⁶²³⁹²¹ is an apocalyptic number.

It is an amenable number.

623921 is a deficient number, since it is larger than the sum of its proper divisors (27151).

623921 is a wasteful number, since it uses less digits than its factorization.

623921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27150.

The product of its digits is 648, while the sum is 23.

The square root of 623921 is about 789.8867007363. The cubic root of 623921 is about 85.4495672848.

The spelling of 623921 in words is "six hundred twenty-three thousand, nine hundred twenty-one".