1661631405 has 24 divisors (see below), whose sum is σ = 3092670432. Its totient is φ = 759602592.

The previous prime is 1661631401. The next prime is 1661631451. The reversal of 1661631405 is 5041361661.

It is not a de Polignac number, because 1661631405 - 2² = 1661631401 is a prime.

It is a super-2 number, since 2×1661631405² = 5522037852164548050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661631401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1129627 + ... + 1131096.

It is an arithmetic number, because the mean of its divisors is an integer number (128861268).

Almost surely, 2^1661631405 is an apocalyptic number.

1661631405 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1661631405 is a deficient number, since it is larger than the sum of its proper divisors (1431039027).

1661631405 is a wasteful number, since it uses less digits than its factorization.

1661631405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2260745 (or 2260738 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 33.

The square root of 1661631405 is about 40763.1132888547. The cubic root of 1661631405 is about 1184.4359044942.

The spelling of 1661631405 in words is "one billion, six hundred sixty-one million, six hundred thirty-one thousand, four hundred five".