28571981 has 4 divisors (see below), whose sum is σ = 28963452. Its totient is φ = 28180512.

The previous prime is 28571969. The next prime is 28571993. The reversal of 28571981 is 18917582.

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

It is an interprime number because it is at equal distance from previous prime (28571969) and next prime (28571993).

It can be written as a sum of positive squares in 2 ways, for example, as 10432900 + 18139081 = 3230^2 + 4259^2 .

It is a cyclic number.

It is not a de Polignac number, because 28571981 - 2¹⁸ = 28309837 is a prime.

It is a super-2 number, since 2×28571981² = 1632716196528722, 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 (28571381) 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, 195626 + ... + 195771.

It is an arithmetic number, because the mean of its divisors is an integer number (7240863).

Almost surely, 2^28571981 is an apocalyptic number.

It is an amenable number.

28571981 is a deficient number, since it is larger than the sum of its proper divisors (391471).

28571981 is an equidigital number, since it uses as much as digits as its factorization.

28571981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 391470.

The product of its digits is 40320, while the sum is 41.

The square root of 28571981 is about 5345.2765129598. The cubic root of 28571981 is about 305.7126790257.

The spelling of 28571981 in words is "twenty-eight million, five hundred seventy-one thousand, nine hundred eighty-one".