21990747 has 8 divisors (see below), whose sum is σ = 29595456. Its totient is φ = 14523272.

The previous prime is 21990721. The next prime is 21990769. The reversal of 21990747 is 74709912.

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

It is a cyclic number.

It is not a de Polignac number, because 21990747 - 2⁸ = 21990491 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21990797) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33933 + ... + 34574.

It is an arithmetic number, because the mean of its divisors is an integer number (3699432).

Almost surely, 2^21990747 is an apocalyptic number.

21990747 is a deficient number, since it is larger than the sum of its proper divisors (7604709).

21990747 is a wasteful number, since it uses less digits than its factorization.

21990747 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68617.

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

The square root of 21990747 is about 4689.4292829725. The cubic root of 21990747 is about 280.1646438145.

The spelling of 21990747 in words is "twenty-one million, nine hundred ninety thousand, seven hundred forty-seven".