1220991 has 16 divisors (see below), whose sum is σ = 1749600. Its totient is φ = 754688.

The previous prime is 1220983. The next prime is 1220993. The reversal of 1220991 is 1990221.

It is a cyclic number.

It is not a de Polignac number, because 1220991 - 2³ = 1220983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1220993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4405 + ... + 4673.

It is an arithmetic number, because the mean of its divisors is an integer number (109350).

2^1220991 is an apocalyptic number.

1220991 is a deficient number, since it is larger than the sum of its proper divisors (528609).

1220991 is a wasteful number, since it uses less digits than its factorization.

1220991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 378.

The product of its (nonzero) digits is 324, while the sum is 24.

The square root of 1220991 is about 1104.9846152775. The cubic root of 1220991 is about 106.8818972328.

It can be divided in two parts, 1220 and 991, that added together give a triangular number (2211 = T₆₆).

The spelling of 1220991 in words is "one million, two hundred twenty thousand, nine hundred ninety-one".