101989781 has 4 divisors (see below), whose sum is σ = 105506700. Its totient is φ = 98472864.

The previous prime is 101989759. The next prime is 101989829. The reversal of 101989781 is 187989101.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 187989101 = 8389 ⋅22409.

It can be written as a sum of positive squares in 2 ways, for example, as 37332100 + 64657681 = 6110^2 + 8041^2 .

It is a de Polignac number, because none of the positive numbers 2^k-101989781 is a prime.

It is a super-2 number, since 2×101989781² = 20803830856855922, 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 (101982781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1758416 + ... + 1758473.

It is an arithmetic number, because the mean of its divisors is an integer number (26376675).

Almost surely, 2^101989781 is an apocalyptic number.

It is an amenable number.

101989781 is a deficient number, since it is larger than the sum of its proper divisors (3516919).

101989781 is an equidigital number, since it uses as much as digits as its factorization.

101989781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3516918.

The product of its (nonzero) digits is 36288, while the sum is 44.

The square root of 101989781 is about 10098.9990098029. Note that the first 3 decimals coincide. The cubic root of 101989781 is about 467.2172688741.

The spelling of 101989781 in words is "one hundred one million, nine hundred eighty-nine thousand, seven hundred eighty-one".