28621991 has 2 divisors, whose sum is σ = 28621992. Its totient is φ = 28621990.

The previous prime is 28621909. The next prime is 28622003. The reversal of 28621991 is 19912682.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28621991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28621891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14310995 + 14310996.

It is an arithmetic number, because the mean of its divisors is an integer number (14310996).

Almost surely, 2^28621991 is an apocalyptic number.

28621991 is a deficient number, since it is larger than the sum of its proper divisors (1).

28621991 is an equidigital number, since it uses as much as digits as its factorization.

28621991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 38.

The square root of 28621991 is about 5349.9524296951. The cubic root of 28621991 is about 305.8909396758.

The spelling of 28621991 in words is "twenty-eight million, six hundred twenty-one thousand, nine hundred ninety-one".