21537601 has 2 divisors, whose sum is σ = 21537602. Its totient is φ = 21537600.

The previous prime is 21537599. The next prime is 21537613. The reversal of 21537601 is 10673512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12531600 + 9006001 = 3540^2 + 3001^2 .

It is a cyclic number.

It is not a de Polignac number, because 21537601 - 2¹ = 21537599 is a prime.

Together with 21537599, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21537631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768800 + 10768801.

It is an arithmetic number, because the mean of its divisors is an integer number (10768801).

Almost surely, 2^21537601 is an apocalyptic number.

It is an amenable number.

21537601 is a deficient number, since it is larger than the sum of its proper divisors (1).

21537601 is an equidigital number, since it uses as much as digits as its factorization.

21537601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21537601 is about 4640.8620966368. The cubic root of 21537601 is about 278.2268949713.

The spelling of 21537601 in words is "twenty-one million, five hundred thirty-seven thousand, six hundred one".