1988817661 has 4 divisors (see below), whose sum is σ = 1994549472. Its totient is φ = 1983085852.

The previous prime is 1988817601. The next prime is 1988817671. The reversal of 1988817661 is 1667188891.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1988817661 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 (1988817601) 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, 2865385 + ... + 2866078.

It is an arithmetic number, because the mean of its divisors is an integer number (498637368).

Almost surely, 2^1988817661 is an apocalyptic number.

It is an amenable number.

1988817661 is a deficient number, since it is larger than the sum of its proper divisors (5731811).

1988817661 is an equidigital number, since it uses as much as digits as its factorization.

1988817661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5731810.

The product of its digits is 1161216, while the sum is 55.

The square root of 1988817661 is about 44596.1619536928. The cubic root of 1988817661 is about 1257.5685159110.

The spelling of 1988817661 in words is "one billion, nine hundred eighty-eight million, eight hundred seventeen thousand, six hundred sixty-one".