20991395 has 8 divisors (see below), whose sum is σ = 25870704. Its totient is φ = 16339104.

The previous prime is 20991361. The next prime is 20991401. The reversal of 20991395 is 59319902.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20991395 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 56549 + ... + 56918.

It is an arithmetic number, because the mean of its divisors is an integer number (3233838).

Almost surely, 2^20991395 is an apocalyptic number.

20991395 is a deficient number, since it is larger than the sum of its proper divisors (4879309).

20991395 is a wasteful number, since it uses less digits than its factorization.

20991395 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113509.

The product of its (nonzero) digits is 21870, while the sum is 38.

The square root of 20991395 is about 4581.6367162838. The cubic root of 20991395 is about 275.8547290890.

The spelling of 20991395 in words is "twenty million, nine hundred ninety-one thousand, three hundred ninety-five".