21617501 has 2 divisors, whose sum is σ = 21617502. Its totient is φ = 21617500.

The previous prime is 21617461. The next prime is 21617503. The reversal of 21617501 is 10571612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14055001 + 7562500 = 3749^2 + 2750^2 .

It is a cyclic number.

It is not a de Polignac number, because 21617501 - 2¹⁰ = 21616477 is a prime.

Together with 21617503, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21617503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10808750 + 10808751.

It is an arithmetic number, because the mean of its divisors is an integer number (10808751).

Almost surely, 2^21617501 is an apocalyptic number.

It is an amenable number.

21617501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21617501 is an equidigital number, since it uses as much as digits as its factorization.

21617501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21617501 is about 4649.4624420464. The cubic root of 21617501 is about 278.5705249399.

The spelling of 21617501 in words is "twenty-one million, six hundred seventeen thousand, five hundred one".