21291057 has 12 divisors (see below), whose sum is σ = 30962100. Its totient is φ = 14097888.

The previous prime is 21291029. The next prime is 21291091. The reversal of 21291057 is 75019212.

It can be written as a sum of positive squares in 2 ways, for example, as 14130081 + 7160976 = 3759^2 + 2676^2 .

It is not a de Polignac number, because 21291057 - 2¹² = 21286961 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21291057.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21291007) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6598 + ... + 9279.

It is an arithmetic number, because the mean of its divisors is an integer number (2580175).

Almost surely, 2^21291057 is an apocalyptic number.

It is an amenable number.

21291057 is a deficient number, since it is larger than the sum of its proper divisors (9671043).

21291057 is a wasteful number, since it uses less digits than its factorization.

21291057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16032 (or 16029 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21291057 is about 4614.2233365974. The cubic root of 21291057 is about 277.1611837604.

The spelling of 21291057 in words is "twenty-one million, two hundred ninety-one thousand, fifty-seven".