921221989 has 4 divisors (see below), whose sum is σ = 943690860. Its totient is φ = 898753120.

The previous prime is 921221969. The next prime is 921222007. The reversal of 921221989 is 989122129.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 989122129 = 167 ⋅5922887.

It can be written as a sum of positive squares in 2 ways, for example, as 186540964 + 734681025 = 13658^2 + 27105^2 .

It is a cyclic number.

It is not a de Polignac number, because 921221989 - 2²¹ = 919124837 is a prime.

It is a super-2 number, since 2×921221989² = 1697299906034232242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (921221969) 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, 11234374 + ... + 11234455.

It is an arithmetic number, because the mean of its divisors is an integer number (235922715).

Almost surely, 2^921221989 is an apocalyptic number.

It is an amenable number.

921221989 is a deficient number, since it is larger than the sum of its proper divisors (22468871).

921221989 is a wasteful number, since it uses less digits than its factorization.

921221989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22468870.

The product of its digits is 46656, while the sum is 43.

The square root of 921221989 is about 30351.6389837518. The cubic root of 921221989 is about 973.0192490559.

The spelling of 921221989 in words is "nine hundred twenty-one million, two hundred twenty-one thousand, nine hundred eighty-nine".