21551973 has 16 divisors (see below), whose sum is σ = 29626560. Its totient is φ = 13929344.

The previous prime is 21551969. The next prime is 21551983. The reversal of 21551973 is 37915512.

It is a cyclic number.

It is not a de Polignac number, because 21551973 - 2² = 21551969 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551923) 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 15 ways as a sum of consecutive naturals, for example, 13390 + ... + 14912.

It is an arithmetic number, because the mean of its divisors is an integer number (1851660).

Almost surely, 2^21551973 is an apocalyptic number.

It is an amenable number.

21551973 is a deficient number, since it is larger than the sum of its proper divisors (8074587).

21551973 is a wasteful number, since it uses less digits than its factorization.

21551973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1668.

The product of its digits is 9450, while the sum is 33.

The square root of 21551973 is about 4642.4102576140. The cubic root of 21551973 is about 278.2887679693.

The spelling of 21551973 in words is "twenty-one million, five hundred fifty-one thousand, nine hundred seventy-three".