1221001998 has 16 divisors (see below), whose sum is σ = 2508004560. Its totient is φ = 396000576.

The previous prime is 1221001987. The next prime is 1221002009. The reversal of 1221001998 is 8991001221.

It is an interprime number because it is at equal distance from previous prime (1221001987) and next prime (1221002009).

It is a congruent 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, 2749783 + ... + 2750226.

It is an arithmetic number, because the mean of its divisors is an integer number (156750285).

Almost surely, 2^1221001998 is an apocalyptic number.

1221001998 is an abundant number, since it is smaller than the sum of its proper divisors (1287002562).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1221001998 is a wasteful number, since it uses less digits than its factorization.

1221001998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5500051.

The product of its (nonzero) digits is 2592, while the sum is 33.

The square root of 1221001998 is about 34942.8390088728. The cubic root of 1221001998 is about 1068.8221814249.

The spelling of 1221001998 in words is "one billion, two hundred twenty-one million, one thousand, nine hundred ninety-eight".