1581220 has 24 divisors (see below), whose sum is σ = 3347064. Its totient is φ = 627456.

The previous prime is 1581211. The next prime is 1581257. The reversal of 1581220 is 221851.

It can be written as a sum of positive squares in 4 ways, for example, as 760384 + 820836 = 872^2 + 906^2 .

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, 3232 + ... + 3688.

It is an arithmetic number, because the mean of its divisors is an integer number (139461).

2^1581220 is an apocalyptic number.

1581220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1581220 is an abundant number, since it is smaller than the sum of its proper divisors (1765844).

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

1581220 is a wasteful number, since it uses less digits than its factorization.

1581220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 639 (or 637 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 19.

The square root of 1581220 is about 1257.4657052978. The cubic root of 1581220 is about 116.5012985911.

It can be divided in two parts, 158 and 1220, that added together give a triangular number (1378 = T₅₂).

The spelling of 1581220 in words is "one million, five hundred eighty-one thousand, two hundred twenty".