1815565961 has 8 divisors (see below), whose sum is σ = 2022758784. Its totient is φ = 1615396720.

The previous prime is 1815565903. The next prime is 1815565979. The reversal of 1815565961 is 1695655181.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1815565961 - 2⁶ = 1815565897 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (47).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1815565901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1755350 + ... + 1756383.

It is an arithmetic number, because the mean of its divisors is an integer number (252844848).

Almost surely, 2^1815565961 is an apocalyptic number.

1815565961 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1815565961 is a deficient number, since it is larger than the sum of its proper divisors (207192823).

1815565961 is a wasteful number, since it uses less digits than its factorization.

1815565961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3511791.

The product of its digits is 324000, while the sum is 47.

The square root of 1815565961 is about 42609.4585860933. The cubic root of 1815565961 is about 1219.9368329294.

The spelling of 1815565961 in words is "one billion, eight hundred fifteen million, five hundred sixty-five thousand, nine hundred sixty-one".