21047655 has 16 divisors (see below), whose sum is σ = 33798240. Its totient is φ = 11184768.

The previous prime is 21047647. The next prime is 21047657. The reversal of 21047655 is 55674012.

It is not a de Polignac number, because 21047655 - 2³ = 21047647 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21047657) 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 15 ways as a sum of consecutive naturals, for example, 2001 + ... + 6789.

It is an arithmetic number, because the mean of its divisors is an integer number (2112390).

Almost surely, 2^21047655 is an apocalyptic number.

21047655 is a deficient number, since it is larger than the sum of its proper divisors (12750585).

21047655 is a wasteful number, since it uses less digits than its factorization.

21047655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5090.

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 21047655 is about 4587.7723352407. The cubic root of 21047655 is about 276.1009528829.

The spelling of 21047655 in words is "twenty-one million, forty-seven thousand, six hundred fifty-five".