1661557001 has 8 divisors (see below), whose sum is σ = 1851071880. Its totient is φ = 1480856832.

The previous prime is 1661556991. The next prime is 1661557031. The reversal of 1661557001 is 1007551661.

It can be written as a sum of positive squares in 4 ways, for example, as 5067001 + 1656490000 = 2251^2 + 40700^2 .

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

It is a de Polignac number, because none of the positive numbers 2^k-1661557001 is a prime.

It is a super-2 number, since 2×1661557001² = 5521543335144228002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661557031) 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, 2203280 + ... + 2204033.

It is an arithmetic number, because the mean of its divisors is an integer number (231383985).

Almost surely, 2^1661557001 is an apocalyptic number.

It is an amenable number.

1661557001 is a deficient number, since it is larger than the sum of its proper divisors (189514879).

1661557001 is a wasteful number, since it uses less digits than its factorization.

1661557001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4407355.

The product of its (nonzero) digits is 6300, while the sum is 32.

The square root of 1661557001 is about 40762.2006398084. The cubic root of 1661557001 is about 1184.4182254662.

The spelling of 1661557001 in words is "one billion, six hundred sixty-one million, five hundred fifty-seven thousand, one".