21229261 has 2 divisors, whose sum is σ = 21229262. Its totient is φ = 21229260.

The previous prime is 21229249. The next prime is 21229297. The reversal of 21229261 is 16292212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18232900 + 2996361 = 4270^2 + 1731^2 .

It is a cyclic number.

It is not a de Polignac number, because 21229261 - 2¹⁵ = 21196493 is a prime.

It is a super-2 number, since 2×21229261² = 901363045212242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21229361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10614630 + 10614631.

It is an arithmetic number, because the mean of its divisors is an integer number (10614631).

Almost surely, 2^21229261 is an apocalyptic number.

It is an amenable number.

21229261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21229261 is an equidigital number, since it uses as much as digits as its factorization.

21229261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 25.

The square root of 21229261 is about 4607.5222191542. The cubic root of 21229261 is about 276.8927760788.

The spelling of 21229261 in words is "twenty-one million, two hundred twenty-nine thousand, two hundred sixty-one".