21145961 has 2 divisors, whose sum is σ = 21145962. Its totient is φ = 21145960.

The previous prime is 21145951. The next prime is 21145973. The reversal of 21145961 is 16954112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20611600 + 534361 = 4540^2 + 731^2 .

It is a cyclic number.

It is not a de Polignac number, because 21145961 - 2²² = 16951657 is a prime.

It is a super-2 number, since 2×21145961² = 894303333227042, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21145921) 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, 10572980 + 10572981.

It is an arithmetic number, because the mean of its divisors is an integer number (10572981).

Almost surely, 2^21145961 is an apocalyptic number.

21145961 is the 2057-th centered decagonal number.

It is an amenable number.

21145961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21145961 is an equidigital number, since it uses as much as digits as its factorization.

21145961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2160, while the sum is 29.

The square root of 21145961 is about 4598.4737685454. The cubic root of 21145961 is about 276.5301413469.

It can be divided in two parts, 2 and 1145961, that multiplied together give a palindrome (2291922).

The spelling of 21145961 in words is "twenty-one million, one hundred forty-five thousand, nine hundred sixty-one".