1221820 has 12 divisors (see below), whose sum is σ = 2565864. Its totient is φ = 488720.

The previous prime is 1221811. The next prime is 1221821. The reversal of 1221820 is 281221.

It is a super-2 number, since 2×1221820² = 2985688224800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1221794 and 1221803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221821) 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, 30526 + ... + 30565.

It is an arithmetic number, because the mean of its divisors is an integer number (213822).

2^1221820 is an apocalyptic number.

1221820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221820 is an abundant number, since it is smaller than the sum of its proper divisors (1344044).

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

1221820 is a wasteful number, since it uses less digits than its factorization.

1221820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61100 (or 61098 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 1221820 is about 1105.3596699717. The cubic root of 1221820 is about 106.9060811532.

The spelling of 1221820 in words is "one million, two hundred twenty-one thousand, eight hundred twenty".