21666900 has 36 divisors (see below), whose sum is σ = 62690432. Its totient is φ = 5777760.

The previous prime is 21666893. The next prime is 21666907. The reversal of 21666900 is 966612.

It is an interprime number because it is at equal distance from previous prime (21666893) and next prime (21666907).

It is a super-2 number, since 2×21666900² = 938909111220000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666907) 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, 35812 + ... + 36411.

Almost surely, 2^21666900 is an apocalyptic number.

21666900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21666900 is an abundant number, since it is smaller than the sum of its proper divisors (41023532).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21666900 is a wasteful number, since it uses less digits than its factorization.

21666900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72240 (or 72233 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 21666900 is about 4654.7717452094. The cubic root of 21666900 is about 278.7825543297.

The spelling of 21666900 in words is "twenty-one million, six hundred sixty-six thousand, nine hundred".