18701981 has 4 divisors (see below), whose sum is σ = 18771264. Its totient is φ = 18632700.

The previous prime is 18701971. The next prime is 18701987. The reversal of 18701981 is 18910781.

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 not a de Polignac number, because 18701981 - 2²² = 14507677 is a prime.

It is a super-2 number, since 2×18701981² = 699528186648722, 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 (18701987) 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, 34235 + ... + 34776.

It is an arithmetic number, because the mean of its divisors is an integer number (4692816).

Almost surely, 2^18701981 is an apocalyptic number.

It is an amenable number.

18701981 is a deficient number, since it is larger than the sum of its proper divisors (69283).

18701981 is an equidigital number, since it uses as much as digits as its factorization.

18701981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69282.

The product of its (nonzero) digits is 4032, while the sum is 35.

The square root of 18701981 is about 4324.5787078050. The cubic root of 18701981 is about 265.4376581851.

The spelling of 18701981 in words is "eighteen million, seven hundred one thousand, nine hundred eighty-one".