21193551 has 12 divisors (see below), whose sum is σ = 30775680. Its totient is φ = 14053920.

The previous prime is 21193541. The next prime is 21193559. The reversal of 21193551 is 15539112.

21193551 is a `hidden beast` number, since 21 + 1 + 93 + 551 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-21193551 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21193559) 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 11 ways as a sum of consecutive naturals, for example, 4446 + ... + 7883.

It is an arithmetic number, because the mean of its divisors is an integer number (2564640).

Almost surely, 2^21193551 is an apocalyptic number.

21193551 is a deficient number, since it is larger than the sum of its proper divisors (9582129).

21193551 is a wasteful number, since it uses less digits than its factorization.

21193551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12526 (or 12523 counting only the distinct ones).

The product of its digits is 1350, while the sum is 27.

The square root of 21193551 is about 4603.6454033733. The cubic root of 21193551 is about 276.7374340350.

The spelling of 21193551 in words is "twenty-one million, one hundred ninety-three thousand, five hundred fifty-one".