1647001561 has 4 divisors (see below), whose sum is σ = 1659574224. Its totient is φ = 1634428900.

The previous prime is 1647001541. The next prime is 1647001583. The reversal of 1647001561 is 1651007461.

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 a de Polignac number, because none of the positive numbers 2^k-1647001561 is a prime.

It is a super-2 number, since 2×1647001561² = 5425228283872873442, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1647001501) 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, 6286135 + ... + 6286396.

It is an arithmetic number, because the mean of its divisors is an integer number (414893556).

Almost surely, 2^1647001561 is an apocalyptic number.

It is an amenable number.

1647001561 is a deficient number, since it is larger than the sum of its proper divisors (12572663).

1647001561 is a wasteful number, since it uses less digits than its factorization.

1647001561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12572662.

The product of its (nonzero) digits is 5040, while the sum is 31.

The square root of 1647001561 is about 40583.2670074749. The cubic root of 1647001561 is about 1180.9495280254.

The spelling of 1647001561 in words is "one billion, six hundred forty-seven million, one thousand, five hundred sixty-one".