28911561 has 32 divisors (see below), whose sum is σ = 46080000. Its totient is φ = 15776640.

The previous prime is 28911557. The next prime is 28911599. The reversal of 28911561 is 16511982.

28911561 is nontrivially palindromic in base 12.

It is not a de Polignac number, because 28911561 - 2² = 28911557 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28911461) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 57690 + ... + 58188.

It is an arithmetic number, because the mean of its divisors is an integer number (1440000).

Almost surely, 2^28911561 is an apocalyptic number.

28911561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

28911561 is a deficient number, since it is larger than the sum of its proper divisors (17168439).

28911561 is a wasteful number, since it uses less digits than its factorization.

28911561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 629.

The product of its digits is 4320, while the sum is 33.

The square root of 28911561 is about 5376.9471821843. The cubic root of 28911561 is about 306.9190511853.

The spelling of 28911561 in words is "twenty-eight million, nine hundred eleven thousand, five hundred sixty-one".