21358537 has 2 divisors, whose sum is σ = 21358538. Its totient is φ = 21358536.

The previous prime is 21358501. The next prime is 21358549. The reversal of 21358537 is 73585312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16232841 + 5125696 = 4029^2 + 2264^2 .

It is a cyclic number.

It is not a de Polignac number, because 21358537 - 2¹⁹ = 20834249 is a prime.

It is not a weakly prime, because it can be changed into another prime (21358577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10679268 + 10679269.

It is an arithmetic number, because the mean of its divisors is an integer number (10679269).

Almost surely, 2^21358537 is an apocalyptic number.

It is an amenable number.

21358537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21358537 is an equidigital number, since it uses as much as digits as its factorization.

21358537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25200, while the sum is 34.

The square root of 21358537 is about 4621.5297251019. The cubic root of 21358537 is about 277.4536870470.

The spelling of 21358537 in words is "twenty-one million, three hundred fifty-eight thousand, five hundred thirty-seven".