21771900 has 108 divisors (see below), whose sum is σ = 72307872. Its totient is φ = 5460480.

The previous prime is 21771859. The next prime is 21771907. The reversal of 21771900 is 917712.

It is a super-2 number, since 2×21771900² = 948031259220000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21771907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 14589 + ... + 16011.

Almost surely, 2^21771900 is an apocalyptic number.

21771900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21771900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36153936).

21771900 is an abundant number, since it is smaller than the sum of its proper divisors (50535972).

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

21771900 is a wasteful number, since it uses less digits than its factorization.

21771900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1460 (or 1450 counting only the distinct ones).

The product of its (nonzero) digits is 882, while the sum is 27.

The square root of 21771900 is about 4666.0368622633. The cubic root of 21771900 is about 279.2321650231.

The spelling of 21771900 in words is "twenty-one million, seven hundred seventy-one thousand, nine hundred".