21971500 has 24 divisors (see below), whose sum is σ = 47986848. Its totient is φ = 8788400.

The previous prime is 21971489. The next prime is 21971501. The reversal of 21971500 is 517912.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is not an unprimeable number, because it can be changed into a prime (21971501) 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 7 ways as a sum of consecutive naturals, for example, 21472 + ... + 22471.

It is an arithmetic number, because the mean of its divisors is an integer number (1999452).

Almost surely, 2^21971500 is an apocalyptic number.

21971500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21971500 is an abundant number, since it is smaller than the sum of its proper divisors (26015348).

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

21971500 is a wasteful number, since it uses less digits than its factorization.

21971500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43962 (or 43950 counting only the distinct ones).

The product of its (nonzero) digits is 630, while the sum is 25.

The square root of 21971500 is about 4687.3766650441. The cubic root of 21971500 is about 280.0828836262.

The spelling of 21971500 in words is "twenty-one million, nine hundred seventy-one thousand, five hundred".