21711861 has 16 divisors (see below), whose sum is σ = 32915520. Its totient is φ = 14137200.

The previous prime is 21711857. The next prime is 21711883. The reversal of 21711861 is 16811712.

It is not a de Polignac number, because 21711861 - 2² = 21711857 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21711841) 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, 8190 + ... + 10511.

It is an arithmetic number, because the mean of its divisors is an integer number (2057220).

Almost surely, 2^21711861 is an apocalyptic number.

It is an amenable number.

21711861 is a deficient number, since it is larger than the sum of its proper divisors (11203659).

21711861 is a wasteful number, since it uses less digits than its factorization.

21711861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18753 (or 18747 counting only the distinct ones).

The product of its digits is 672, while the sum is 27.

The square root of 21711861 is about 4659.5988024722. The cubic root of 21711861 is about 278.9752550606.

The spelling of 21711861 in words is "twenty-one million, seven hundred eleven thousand, eight hundred sixty-one".