21504861 has 12 divisors (see below), whose sum is σ = 35500192. Its totient is φ = 12288456.

The previous prime is 21504841. The next prime is 21504871. The reversal of 21504861 is 16840512.

It is not a de Polignac number, because 21504861 - 2⁹ = 21504349 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21504841) 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 in 11 ways as a sum of consecutive naturals, for example, 170611 + ... + 170736.

Almost surely, 2^21504861 is an apocalyptic number.

21504861 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21504861 is a deficient number, since it is larger than the sum of its proper divisors (13995331).

21504861 is a wasteful number, since it uses less digits than its factorization.

21504861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 341360 (or 341357 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21504861 is about 4637.3333932337. Note that the first 4 decimals coincide. The cubic root of 21504861 is about 278.0858429240.

The spelling of 21504861 in words is "twenty-one million, five hundred four thousand, eight hundred sixty-one".