21730537 has 2 divisors, whose sum is σ = 21730538. Its totient is φ = 21730536.

The previous prime is 21730531. The next prime is 21730543. The reversal of 21730537 is 73503712.

It is a balanced prime because it is at equal distance from previous prime (21730531) and next prime (21730543).

It can be written as a sum of positive squares in only one way, i.e., 18826921 + 2903616 = 4339^2 + 1704^2 .

It is a cyclic number.

It is not a de Polignac number, because 21730537 - 2¹⁹ = 21206249 is a prime.

It is not a weakly prime, because it can be changed into another prime (21730531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865268 + 10865269.

It is an arithmetic number, because the mean of its divisors is an integer number (10865269).

Almost surely, 2^21730537 is an apocalyptic number.

It is an amenable number.

21730537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21730537 is an equidigital number, since it uses as much as digits as its factorization.

21730537 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4410, while the sum is 28.

The square root of 21730537 is about 4661.6024068983. The cubic root of 21730537 is about 279.0552213165.

The spelling of 21730537 in words is "twenty-one million, seven hundred thirty thousand, five hundred thirty-seven".