21801866 has 8 divisors (see below), whose sum is σ = 33757824. Its totient is φ = 10549260.

The previous prime is 21801851. The next prime is 21801869. The reversal of 21801866 is 66810812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21801866² = 950642722163912, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21801869) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 175760 + ... + 175883.

It is an arithmetic number, because the mean of its divisors is an integer number (4219728).

Almost surely, 2^21801866 is an apocalyptic number.

21801866 is a deficient number, since it is larger than the sum of its proper divisors (11955958).

21801866 is a wasteful number, since it uses less digits than its factorization.

21801866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 351676.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21801866 is about 4669.2468343406. The cubic root of 21801866 is about 279.3602144063.

The spelling of 21801866 in words is "twenty-one million, eight hundred one thousand, eight hundred sixty-six".