21550961 has 4 divisors (see below), whose sum is σ = 21645300. Its totient is φ = 21456624.

The previous prime is 21550939. The next prime is 21551039. The reversal of 21550961 is 16905512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9265936 + 12285025 = 3044^2 + 3505^2 .

It is a cyclic number.

It is not a de Polignac number, because 21550961 - 2¹⁴ = 21534577 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21550901) 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 in 3 ways as a sum of consecutive naturals, for example, 46826 + ... + 47283.

It is an arithmetic number, because the mean of its divisors is an integer number (5411325).

Almost surely, 2^21550961 is an apocalyptic number.

It is an amenable number.

21550961 is a deficient number, since it is larger than the sum of its proper divisors (94339).

21550961 is an equidigital number, since it uses as much as digits as its factorization.

21550961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94338.

The product of its (nonzero) digits is 2700, while the sum is 29.

The square root of 21550961 is about 4642.3012612281. The cubic root of 21550961 is about 278.2844121014.

The spelling of 21550961 in words is "twenty-one million, five hundred fifty thousand, nine hundred sixty-one".