28391921 has 8 divisors (see below), whose sum is σ = 30572640. Its totient is φ = 26267968.

The previous prime is 28391903. The next prime is 28391929. The reversal of 28391921 is 12919382.

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 28391921 - 2²² = 24197617 is a prime.

It is a super-2 number, since 2×28391921² = 1612202356140482, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28391929) 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, 13151 + ... + 15156.

It is an arithmetic number, because the mean of its divisors is an integer number (3821580).

Almost surely, 2^28391921 is an apocalyptic number.

It is an amenable number.

28391921 is a deficient number, since it is larger than the sum of its proper divisors (2180719).

28391921 is a wasteful number, since it uses less digits than its factorization.

28391921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28383.

The product of its digits is 7776, while the sum is 35.

The square root of 28391921 is about 5328.4069852067. The cubic root of 28391921 is about 305.0691270350.

The spelling of 28391921 in words is "twenty-eight million, three hundred ninety-one thousand, nine hundred twenty-one".