991221004 has 24 divisors (see below), whose sum is σ = 1771837200. Its totient is φ = 485056320.

The previous prime is 991220983. The next prime is 991221019. The reversal of 991221004 is 400122199.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44874 + ... + 63214.

It is an arithmetic number, because the mean of its divisors is an integer number (73826550).

Almost surely, 2^991221004 is an apocalyptic number.

It is an amenable number.

991221004 is a deficient number, since it is larger than the sum of its proper divisors (780616196).

991221004 is a wasteful number, since it uses less digits than its factorization.

991221004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18633 (or 18631 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 991221004 is about 31483.6624934267. The cubic root of 991221004 is about 997.0650625693.

The spelling of 991221004 in words is "nine hundred ninety-one million, two hundred twenty-one thousand, four".