1561551001 has 8 divisors (see below), whose sum is σ = 1582652808. Its totient is φ = 1540560000.

The previous prime is 1561550981. The next prime is 1561551011. The reversal of 1561551001 is 1001551651.

It can be written as a sum of positive squares in 4 ways, for example, as 588111001 + 973440000 = 24251^2 + 31200^2 .

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 1561551001 - 2⁹ = 1561550489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561551011) 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, 871 + ... + 55891.

It is an arithmetic number, because the mean of its divisors is an integer number (197831601).

Almost surely, 2^1561551001 is an apocalyptic number.

It is an amenable number.

1561551001 is a deficient number, since it is larger than the sum of its proper divisors (21101807).

1561551001 is a wasteful number, since it uses less digits than its factorization.

1561551001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55403.

The product of its (nonzero) digits is 750, while the sum is 25.

The square root of 1561551001 is about 39516.4649355177. The cubic root of 1561551001 is about 1160.1622347904.

The spelling of 1561551001 in words is "one billion, five hundred sixty-one million, five hundred fifty-one thousand, one".