1615651561 has 4 divisors (see below), whose sum is σ = 1616387152. Its totient is φ = 1614915972.

The previous prime is 1615651553. The next prime is 1615651571. The reversal of 1615651561 is 1651565161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1615651561 - 2³ = 1615651553 is a prime.

It is a super-2 number, since 2×1615651561² = 5220659933123473442, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1615651561.

It is not an unprimeable number, because it can be changed into a prime (1615651501) 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, 364491 + ... + 368896.

It is an arithmetic number, because the mean of its divisors is an integer number (404096788).

Almost surely, 2^1615651561 is an apocalyptic number.

It is an amenable number.

1615651561 is a deficient number, since it is larger than the sum of its proper divisors (735591).

1615651561 is an equidigital number, since it uses as much as digits as its factorization.

1615651561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 735590.

The product of its digits is 27000, while the sum is 37.

The square root of 1615651561 is about 40195.1683787990. The cubic root of 1615651561 is about 1173.4085134891.

The spelling of 1615651561 in words is "one billion, six hundred fifteen million, six hundred fifty-one thousand, five hundred sixty-one".