21012261 has 4 divisors (see below), whose sum is σ = 28016352. Its totient is φ = 14008172.

The previous prime is 21012259. The next prime is 21012281. The reversal of 21012261 is 16221012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21012261 - 2¹ = 21012259 is a prime.

It is a super-2 number, since 2×21012261² = 883030224664242, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21012261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012241) 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 in 3 ways as a sum of consecutive naturals, for example, 3502041 + ... + 3502046.

It is an arithmetic number, because the mean of its divisors is an integer number (7004088).

Almost surely, 2^21012261 is an apocalyptic number.

It is an amenable number.

21012261 is a deficient number, since it is larger than the sum of its proper divisors (7004091).

21012261 is an equidigital number, since it uses as much as digits as its factorization.

21012261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7004090.

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 21012261 is about 4583.9132845201. The cubic root of 21012261 is about 275.9461011112.

Adding to 21012261 its reverse (16221012), we get a palindrome (37233273).

The spelling of 21012261 in words is "twenty-one million, twelve thousand, two hundred sixty-one".