921561 has 4 divisors (see below), whose sum is σ = 1228752. Its totient is φ = 614372.

The previous prime is 921523. The next prime is 921563. The reversal of 921561 is 165129.

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 921561 - 2⁶ = 921497 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (921563) 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, 153591 + ... + 153596.

It is an arithmetic number, because the mean of its divisors is an integer number (307188).

2⁹²¹⁵⁶¹ is an apocalyptic number.

It is an amenable number.

921561 is a deficient number, since it is larger than the sum of its proper divisors (307191).

921561 is a wasteful number, since it uses less digits than its factorization.

921561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 307190.

The product of its digits is 540, while the sum is 24.

The square root of 921561 is about 959.9796872851. The cubic root of 921561 is about 97.3138591906.

It can be divided in two parts, 92 and 1561, that added together give a triangular number (1653 = T₅₇).

The spelling of 921561 in words is "nine hundred twenty-one thousand, five hundred sixty-one".