921231551 has 4 divisors (see below), whose sum is σ = 922993512. Its totient is φ = 919469592.

The previous prime is 921231529. The next prime is 921231593. The reversal of 921231551 is 155132129.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 921231551 - 2¹⁴ = 921215167 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (921231851) 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, 880196 + ... + 881241.

It is an arithmetic number, because the mean of its divisors is an integer number (230748378).

Almost surely, 2^921231551 is an apocalyptic number.

921231551 is a deficient number, since it is larger than the sum of its proper divisors (1761961).

921231551 is a wasteful number, since it uses less digits than its factorization.

921231551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1761960.

The product of its digits is 2700, while the sum is 29.

The square root of 921231551 is about 30351.7965036668. The cubic root of 921231551 is about 973.0226155908.

The spelling of 921231551 in words is "nine hundred twenty-one million, two hundred thirty-one thousand, five hundred fifty-one".