21997740 has 48 divisors (see below), whose sum is σ = 61901280. Its totient is φ = 5836800.

The previous prime is 21997733. The next prime is 21997751. The reversal of 21997740 is 4779912.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 12940 + ... + 14540.

It is an arithmetic number, because the mean of its divisors is an integer number (1289610).

Almost surely, 2^21997740 is an apocalyptic number.

21997740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21997740 is an abundant number, since it is smaller than the sum of its proper divisors (39903540).

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

21997740 is a wasteful number, since it uses less digits than its factorization.

21997740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1842 (or 1840 counting only the distinct ones).

The product of its (nonzero) digits is 31752, while the sum is 39.

The square root of 21997740 is about 4690.1748368264. The cubic root of 21997740 is about 280.1943378750.

The spelling of 21997740 in words is "twenty-one million, nine hundred ninety-seven thousand, seven hundred forty".