21007501 has 2 divisors, whose sum is σ = 21007502. Its totient is φ = 21007500.

The previous prime is 21007499. The next prime is 21007523. The reversal of 21007501 is 10570012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16281225 + 4726276 = 4035^2 + 2174^2 .

It is a cyclic number.

It is not a de Polignac number, because 21007501 - 2¹ = 21007499 is a prime.

Together with 21007499, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21007531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503750 + 10503751.

It is an arithmetic number, because the mean of its divisors is an integer number (10503751).

Almost surely, 2^21007501 is an apocalyptic number.

It is an amenable number.

21007501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21007501 is an equidigital number, since it uses as much as digits as its factorization.

21007501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 70, while the sum is 16.

The square root of 21007501 is about 4583.3940480827. The cubic root of 21007501 is about 275.9252624425.

Adding to 21007501 its reverse (10570012), we get a palindrome (31577513).

The spelling of 21007501 in words is "twenty-one million, seven thousand, five hundred one".