20901591 has 8 divisors (see below), whose sum is σ = 30965360. Its totient is φ = 13934376.

The previous prime is 20901581. The next prime is 20901599. The reversal of 20901591 is 19510902.

It is a happy number.

It is not a de Polignac number, because 20901591 - 2⁹ = 20901079 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 774133 = 20901591 / (2 + 0 + 9 + 0 + 1 + 5 + 9 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20901599) 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, 387040 + ... + 387093.

It is an arithmetic number, because the mean of its divisors is an integer number (3870670).

Almost surely, 2^20901591 is an apocalyptic number.

20901591 is a deficient number, since it is larger than the sum of its proper divisors (10063769).

20901591 is an equidigital number, since it uses as much as digits as its factorization.

20901591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 774142 (or 774136 counting only the distinct ones).

The product of its (nonzero) digits is 810, while the sum is 27.

The square root of 20901591 is about 4571.8257840823. The cubic root of 20901591 is about 275.4607856105.

The spelling of 20901591 in words is "twenty million, nine hundred one thousand, five hundred ninety-one".