21037813 has 2 divisors, whose sum is σ = 21037814. Its totient is φ = 21037812.

The previous prime is 21037781. The next prime is 21037817. The reversal of 21037813 is 31873012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19731364 + 1306449 = 4442^2 + 1143^2 .

It is a cyclic number.

It is not a de Polignac number, because 21037813 - 2⁵ = 21037781 is a prime.

It is a super-3 number, since 3×21037813³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21037817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10518906 + 10518907.

It is an arithmetic number, because the mean of its divisors is an integer number (10518907).

Almost surely, 2^21037813 is an apocalyptic number.

It is an amenable number.

21037813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21037813 is an equidigital number, since it uses as much as digits as its factorization.

21037813 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21037813 is about 4586.6995759478. The cubic root of 21037813 is about 276.0579107286.

The spelling of 21037813 in words is "twenty-one million, thirty-seven thousand, eight hundred thirteen".