28671781 has 8 divisors (see below), whose sum is σ = 30004344. Its totient is φ = 27368640.

The previous prime is 28671767. The next prime is 28671787. The reversal of 28671781 is 18717682.

It can be written as a sum of positive squares in 4 ways, for example, as 3330625 + 25341156 = 1825^2 + 5034^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 28671781 - 2⁷ = 28671653 is a prime.

It is a super-2 number, since 2×28671781² = 1644142051423922, 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 (28671787) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5350 + ... + 9271.

It is an arithmetic number, because the mean of its divisors is an integer number (3750543).

Almost surely, 2^28671781 is an apocalyptic number.

It is an amenable number.

28671781 is a deficient number, since it is larger than the sum of its proper divisors (1332563).

28671781 is a wasteful number, since it uses less digits than its factorization.

28671781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14711.

The product of its digits is 37632, while the sum is 40.

The square root of 28671781 is about 5354.6037201645. The cubic root of 28671781 is about 306.0682099783.

The spelling of 28671781 in words is "twenty-eight million, six hundred seventy-one thousand, seven hundred eighty-one".