21485991 has 4 divisors (see below), whose sum is σ = 28647992. Its totient is φ = 14323992.

The previous prime is 21485957. The next prime is 21485993. The reversal of 21485991 is 19958412.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21485991 - 2¹⁴ = 21469607 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21485993) 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, 3580996 + ... + 3581001.

It is an arithmetic number, because the mean of its divisors is an integer number (7161998).

Almost surely, 2^21485991 is an apocalyptic number.

21485991 is a deficient number, since it is larger than the sum of its proper divisors (7162001).

21485991 is an equidigital number, since it uses as much as digits as its factorization.

21485991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7162000.

The product of its digits is 25920, while the sum is 39.

The square root of 21485991 is about 4635.2983722734. The cubic root of 21485991 is about 278.0044812348.

The spelling of 21485991 in words is "twenty-one million, four hundred eighty-five thousand, nine hundred ninety-one".