21290501 has 2 divisors, whose sum is σ = 21290502. Its totient is φ = 21290500.

The previous prime is 21290449. The next prime is 21290509. The reversal of 21290501 is 10509212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15880225 + 5410276 = 3985^2 + 2326^2 .

It is a cyclic number.

It is not a de Polignac number, because 21290501 - 2²² = 17096197 is a prime.

It is a Sophie Germain prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21290509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10645250 + 10645251.

It is an arithmetic number, because the mean of its divisors is an integer number (10645251).

Almost surely, 2^21290501 is an apocalyptic number.

It is an amenable number.

21290501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21290501 is an equidigital number, since it uses as much as digits as its factorization.

21290501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 21290501 is about 4614.1630877116. The cubic root of 21290501 is about 277.1587711206.

Adding to 21290501 its reverse (10509212), we get a palindrome (31799713).

The spelling of 21290501 in words is "twenty-one million, two hundred ninety thousand, five hundred one".