21591049 has 6 divisors (see below), whose sum is σ = 22787610. Its totient is φ = 20454336.

The previous prime is 21591041. The next prime is 21591067. The reversal of 21591049 is 94019512.

It can be written as a sum of positive squares in only one way, i.e., 20793600 + 797449 = 4560^2 + 893^2 .

It is not a de Polignac number, because 21591049 - 2³ = 21591041 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21591049.

It is not an unprimeable number, because it can be changed into a prime (21591041) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 29544 + ... + 30265.

It is an arithmetic number, because the mean of its divisors is an integer number (3797935).

Almost surely, 2^21591049 is an apocalyptic number.

It is an amenable number.

21591049 is a deficient number, since it is larger than the sum of its proper divisors (1196561).

21591049 is an equidigital number, since it uses as much as digits as its factorization.

21591049 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59847 (or 59828 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 31.

The square root of 21591049 is about 4646.6169413886. The cubic root of 21591049 is about 278.4568553853.

The spelling of 21591049 in words is "twenty-one million, five hundred ninety-one thousand, forty-nine".