20988391 has 2 divisors, whose sum is σ = 20988392. Its totient is φ = 20988390.

The previous prime is 20988377. The next prime is 20988403. The reversal of 20988391 is 19388902.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20988391 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20988301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10494195 + 10494196.

It is an arithmetic number, because the mean of its divisors is an integer number (10494196).

Almost surely, 2^20988391 is an apocalyptic number.

20988391 is a deficient number, since it is larger than the sum of its proper divisors (1).

20988391 is an equidigital number, since it uses as much as digits as its factorization.

20988391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 20988391 is about 4581.3088741101. The cubic root of 20988391 is about 275.8415696152.

The spelling of 20988391 in words is "twenty million, nine hundred eighty-eight thousand, three hundred ninety-one".