21952561 has 8 divisors (see below), whose sum is σ = 22374144. Its totient is φ = 21534240.

The previous prime is 21952549. The next prime is 21952571. The reversal of 21952561 is 16525912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21952561 - 2⁵ = 21952529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21952501) 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 7 ways as a sum of consecutive naturals, for example, 15880 + ... + 17206.

It is an arithmetic number, because the mean of its divisors is an integer number (2796768).

Almost surely, 2^21952561 is an apocalyptic number.

It is an amenable number.

21952561 is a deficient number, since it is larger than the sum of its proper divisors (421583).

21952561 is a wasteful number, since it uses less digits than its factorization.

21952561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1631.

The product of its digits is 5400, while the sum is 31.

The square root of 21952561 is about 4685.3560163556. The cubic root of 21952561 is about 280.0023851838.

The spelling of 21952561 in words is "twenty-one million, nine hundred fifty-two thousand, five hundred sixty-one".