21542537 has 2 divisors, whose sum is σ = 21542538. Its totient is φ = 21542536.

The previous prime is 21542483. The next prime is 21542579. The reversal of 21542537 is 73524512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17397241 + 4145296 = 4171^2 + 2036^2 .

It is a cyclic number.

It is not a de Polignac number, because 21542537 - 2¹⁸ = 21280393 is a prime.

It is not a weakly prime, because it can be changed into another prime (21542597) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771268 + 10771269.

It is an arithmetic number, because the mean of its divisors is an integer number (10771269).

Almost surely, 2^21542537 is an apocalyptic number.

It is an amenable number.

21542537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21542537 is an equidigital number, since it uses as much as digits as its factorization.

21542537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8400, while the sum is 29.

The square root of 21542537 is about 4641.3938639163. The cubic root of 21542537 is about 278.2481480820.

The spelling of 21542537 in words is "twenty-one million, five hundred forty-two thousand, five hundred thirty-seven".