21056437 has 2 divisors, whose sum is σ = 21056438. Its totient is φ = 21056436.

The previous prime is 21056401. The next prime is 21056447. The reversal of 21056437 is 73465012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13024881 + 8031556 = 3609^2 + 2834^2 .

It is a cyclic number.

It is not a de Polignac number, because 21056437 - 2²³ = 12667829 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21056447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10528218 + 10528219.

It is an arithmetic number, because the mean of its divisors is an integer number (10528219).

Almost surely, 2^21056437 is an apocalyptic number.

It is an amenable number.

21056437 is a deficient number, since it is larger than the sum of its proper divisors (1).

21056437 is an equidigital number, since it uses as much as digits as its factorization.

21056437 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5040, while the sum is 28.

The square root of 21056437 is about 4588.7293448187. The cubic root of 21056437 is about 276.1393479981.

The spelling of 21056437 in words is "twenty-one million, fifty-six thousand, four hundred thirty-seven".