21668047 has 16 divisors (see below), whose sum is σ = 24164352. Its totient is φ = 19324800.

The previous prime is 21668033. The next prime is 21668099. The reversal of 21668047 is 74086612.

It is a cyclic number.

It is not a de Polignac number, because 21668047 - 2¹⁵ = 21635279 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668147) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 58858 + ... + 59224.

It is an arithmetic number, because the mean of its divisors is an integer number (1510272).

Almost surely, 2^21668047 is an apocalyptic number.

21668047 is a deficient number, since it is larger than the sum of its proper divisors (2496305).

21668047 is a wasteful number, since it uses less digits than its factorization.

21668047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 558.

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 21668047 is about 4654.8949504795. The cubic root of 21668047 is about 278.7874736297.

The spelling of 21668047 in words is "twenty-one million, six hundred sixty-eight thousand, forty-seven".