918193921 has 4 divisors (see below), whose sum is σ = 939547312. Its totient is φ = 896840532.

The previous prime is 918193909. The next prime is 918193963. The reversal of 918193921 is 129391819.

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: 129391819 = 6121 ⋅21139.

It is a cyclic number.

It is not a de Polignac number, because 918193921 - 2¹³ = 918185729 is a prime.

It is a super-3 number, since 3×918193921³ (a number of 28 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Harshad number since it is a multiple of its sum of digits (43), and also a Moran number because the ratio is a prime number: 21353347 = 918193921 / (9 + 1 + 8 + 1 + 9 + 3 + 9 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (918193901) 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, 10676631 + ... + 10676716.

It is an arithmetic number, because the mean of its divisors is an integer number (234886828).

Almost surely, 2^918193921 is an apocalyptic number.

It is an amenable number.

918193921 is a deficient number, since it is larger than the sum of its proper divisors (21353391).

918193921 is a wasteful number, since it uses less digits than its factorization.

918193921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21353390.

The product of its digits is 34992, while the sum is 43.

The square root of 918193921 is about 30301.7148194620. The cubic root of 918193921 is about 971.9519700705.

The spelling of 918193921 in words is "nine hundred eighteen million, one hundred ninety-three thousand, nine hundred twenty-one".