21997506 has 8 divisors (see below), whose sum is σ = 43995024. Its totient is φ = 7332500.

The previous prime is 21997487. The next prime is 21997513. The reversal of 21997506 is 60579912.

It is a sphenic number, since it is the product of 3 distinct primes.

21997506 is an admirable number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1833120 + ... + 1833131.

It is an arithmetic number, because the mean of its divisors is an integer number (5499378).

Almost surely, 2^21997506 is an apocalyptic number.

21997506 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21997506 is a wasteful number, since it uses less digits than its factorization.

21997506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3666256.

The product of its (nonzero) digits is 34020, while the sum is 39.

The square root of 21997506 is about 4690.1498909950. The cubic root of 21997506 is about 280.1933443531.

The spelling of 21997506 in words is "twenty-one million, nine hundred ninety-seven thousand, five hundred six".