921551 has 4 divisors (see below), whose sum is σ = 923472. Its totient is φ = 919632.

The previous prime is 921523. The next prime is 921563. The reversal of 921551 is 155129.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 155129 = 13 ⋅11933.

It is a cyclic number.

It is not a de Polignac number, because 921551 - 2¹⁴ = 905167 is a prime.

It is a Duffinian number.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (921581) 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, 470 + ... + 1436.

It is an arithmetic number, because the mean of its divisors is an integer number (230868).

2⁹²¹⁵⁵¹ is an apocalyptic number.

921551 is a deficient number, since it is larger than the sum of its proper divisors (1921).

921551 is an equidigital number, since it uses as much as digits as its factorization.

921551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1920.

The product of its digits is 450, while the sum is 23.

The square root of 921551 is about 959.9744788274. The cubic root of 921551 is about 97.3135072001.

It can be divided in two parts, 9215 and 51, that multiplied together give a triangular number (469965 = T₉₆₉).

The spelling of 921551 in words is "nine hundred twenty-one thousand, five hundred fifty-one".