21537497 has 2 divisors, whose sum is σ = 21537498. Its totient is φ = 21537496.

The previous prime is 21537493. The next prime is 21537541. The reversal of 21537497 is 79473512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10916416 + 10621081 = 3304^2 + 3259^2 .

It is a cyclic number.

It is not a de Polignac number, because 21537497 - 2² = 21537493 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21537497.

It is not a weakly prime, because it can be changed into another prime (21537491) 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, 10768748 + 10768749.

It is an arithmetic number, because the mean of its divisors is an integer number (10768749).

Almost surely, 2^21537497 is an apocalyptic number.

It is an amenable number.

21537497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21537497 is an equidigital number, since it uses as much as digits as its factorization.

21537497 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 52920, while the sum is 38.

The square root of 21537497 is about 4640.8508918085. The cubic root of 21537497 is about 278.2264471399.

The spelling of 21537497 in words is "twenty-one million, five hundred thirty-seven thousand, four hundred ninety-seven".