21006737 has 2 divisors, whose sum is σ = 21006738. Its totient is φ = 21006736.

The previous prime is 21006731. The next prime is 21006743. The reversal of 21006737 is 73760012.

It is a balanced prime because it is at equal distance from previous prime (21006731) and next prime (21006743).

It can be written as a sum of positive squares in only one way, i.e., 20647936 + 358801 = 4544^2 + 599^2 .

It is a cyclic number.

It is not a de Polignac number, because 21006737 - 2⁶ = 21006673 is a prime.

It is not a weakly prime, because it can be changed into another prime (21006731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503368 + 10503369.

It is an arithmetic number, because the mean of its divisors is an integer number (10503369).

Almost surely, 2^21006737 is an apocalyptic number.

It is an amenable number.

21006737 is a deficient number, since it is larger than the sum of its proper divisors (1).

21006737 is an equidigital number, since it uses as much as digits as its factorization.

21006737 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1764, while the sum is 26.

The square root of 21006737 is about 4583.3107029744. The cubic root of 21006737 is about 275.9219174554.

Adding to 21006737 its reverse (73760012), we get a palindrome (94766749).

The spelling of 21006737 in words is "twenty-one million, six thousand, seven hundred thirty-seven".