28071661 has 4 divisors (see below), whose sum is σ = 29292192. Its totient is φ = 26851132.

The previous prime is 28071653. The next prime is 28071671. The reversal of 28071661 is 16617082.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16617082 = 2 ⋅8308541.

It is a cyclic number.

It is not a de Polignac number, because 28071661 - 2³ = 28071653 is a prime.

It is a super-3 number, since 3×28071661³ (a number of 23 digits) contains 333 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 (28071601) 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, 610231 + ... + 610276.

It is an arithmetic number, because the mean of its divisors is an integer number (7323048).

Almost surely, 2^28071661 is an apocalyptic number.

It is an amenable number.

28071661 is a deficient number, since it is larger than the sum of its proper divisors (1220531).

28071661 is a wasteful number, since it uses less digits than its factorization.

28071661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1220530.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 28071661 is about 5298.2696231883. The cubic root of 28071661 is about 303.9177300750.

The spelling of 28071661 in words is "twenty-eight million, seventy-one thousand, six hundred sixty-one".