20991093 has 8 divisors (see below), whose sum is σ = 28583808. Its totient is φ = 13696224.

The previous prime is 20991083. The next prime is 20991097. The reversal of 20991093 is 39019902.

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

It is not a de Polignac number, because 20991093 - 2¹⁸ = 20728949 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20991097) 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, 74296 + ... + 74577.

It is an arithmetic number, because the mean of its divisors is an integer number (3572976).

Almost surely, 2^20991093 is an apocalyptic number.

It is an amenable number.

20991093 is a deficient number, since it is larger than the sum of its proper divisors (7592715).

20991093 is a wasteful number, since it uses less digits than its factorization.

20991093 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148923.

The product of its (nonzero) digits is 4374, while the sum is 33.

The square root of 20991093 is about 4581.6037585108. The cubic root of 20991093 is about 275.8534061894.

The spelling of 20991093 in words is "twenty million, nine hundred ninety-one thousand, ninety-three".