1661420671 has 4 divisors (see below), whose sum is σ = 1663430472. Its totient is φ = 1659410872.

The previous prime is 1661420653. The next prime is 1661420687. The reversal of 1661420671 is 1760241661.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1661420671 - 2¹¹ = 1661418623 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 (1661420611) 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, 1003660 + ... + 1005313.

It is an arithmetic number, because the mean of its divisors is an integer number (415857618).

Almost surely, 2^1661420671 is an apocalyptic number.

1661420671 is a deficient number, since it is larger than the sum of its proper divisors (2009801).

1661420671 is an equidigital number, since it uses as much as digits as its factorization.

1661420671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2009800.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 1661420671 is about 40760.5283454471. The cubic root of 1661420671 is about 1184.3858309204.

The spelling of 1661420671 in words is "one billion, six hundred sixty-one million, four hundred twenty thousand, six hundred seventy-one".