1661417621 has 4 divisors (see below), whose sum is σ = 1701940044. Its totient is φ = 1620895200.

The previous prime is 1661417591. The next prime is 1661417629. The reversal of 1661417621 is 1267141661.

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

It can be written as a sum of positive squares in 2 ways, for example, as 561168721 + 1100248900 = 23689^2 + 33170^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661417621 - 2²² = 1657223317 is a prime.

It is a super-2 number, since 2×1661417621² = 5520617022738599282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661417629) 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, 20261150 + ... + 20261231.

It is an arithmetic number, because the mean of its divisors is an integer number (425485011).

Almost surely, 2^1661417621 is an apocalyptic number.

It is an amenable number.

1661417621 is a deficient number, since it is larger than the sum of its proper divisors (40522423).

1661417621 is an equidigital number, since it uses as much as digits as its factorization.

1661417621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40522422.

The product of its digits is 12096, while the sum is 35.

The square root of 1661417621 is about 40760.4909317834. The cubic root of 1661417621 is about 1184.3851061634.

The spelling of 1661417621 in words is "one billion, six hundred sixty-one million, four hundred seventeen thousand, six hundred twenty-one".