1815121920 has 208 divisors, whose sum is σ = 6001316352. Its totient is φ = 467927040.

The previous prime is 1815121901. The next prime is 1815121939. The reversal of 1815121920 is 291215181.

It is an interprime number because it is at equal distance from previous prime (1815121901) and next prime (1815121939).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1904164 + ... + 1905116.

Almost surely, 2^1815121920 is an apocalyptic number.

1815121920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1815121920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3000658176).

1815121920 is an abundant number, since it is smaller than the sum of its proper divisors (4186194432).

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

1815121920 is an equidigital number, since it uses as much as digits as its factorization.

1815121920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1016 (or 994 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 30.

The square root of 1815121920 is about 42604.2476755546. The cubic root of 1815121920 is about 1219.8373697040.

The spelling of 1815121920 in words is "one billion, eight hundred fifteen million, one hundred twenty-one thousand, nine hundred twenty".