21971800 has 24 divisors (see below), whose sum is σ = 51084900. Its totient is φ = 8788640.

The previous prime is 21971797. The next prime is 21971801. The reversal of 21971800 is 817912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21971801) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 54730 + ... + 55129.

Almost surely, 2^21971800 is an apocalyptic number.

21971800 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21971800 is an abundant number, since it is smaller than the sum of its proper divisors (29113100).

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

21971800 is a wasteful number, since it uses less digits than its factorization.

21971800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109875 (or 109866 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21971800 is about 4687.4086657769. The cubic root of 21971800 is about 280.0841583758.

The spelling of 21971800 in words is "twenty-one million, nine hundred seventy-one thousand, eight hundred".