21671501 has 2 divisors, whose sum is σ = 21671502. Its totient is φ = 21671500.

The previous prime is 21671491. The next prime is 21671513. The reversal of 21671501 is 10517612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19272100 + 2399401 = 4390^2 + 1549^2 .

It is a cyclic number.

It is not a de Polignac number, because 21671501 - 2¹⁰ = 21670477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21671521) 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, 10835750 + 10835751.

It is an arithmetic number, because the mean of its divisors is an integer number (10835751).

Almost surely, 2^21671501 is an apocalyptic number.

It is an amenable number.

21671501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21671501 is an equidigital number, since it uses as much as digits as its factorization.

21671501 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 21671501 is about 4655.2659429940. The cubic root of 21671501 is about 278.8022862364.

It can be divided in two parts, 216 and 71501, that added together give a palindrome (71717).

The spelling of 21671501 in words is "twenty-one million, six hundred seventy-one thousand, five hundred one".