1565400661 has 8 divisors (see below), whose sum is σ = 1709252064. Its totient is φ = 1421806320.

The previous prime is 1565400649. The next prime is 1565400673. The reversal of 1565400661 is 1660045651.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1565400649) and next prime (1565400673).

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

It is not a de Polignac number, because 1565400661 - 2²⁷ = 1431182933 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1565400611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 51415 + ... + 75988.

It is an arithmetic number, because the mean of its divisors is an integer number (213656508).

Almost surely, 2^1565400661 is an apocalyptic number.

1565400661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1565400661 is a deficient number, since it is larger than the sum of its proper divisors (143851403).

1565400661 is a wasteful number, since it uses less digits than its factorization.

1565400661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128531.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 1565400661 is about 39565.1445214092. The cubic root of 1565400661 is about 1161.1148272226.

The spelling of 1565400661 in words is "one billion, five hundred sixty-five million, four hundred thousand, six hundred sixty-one".