20151881 has 2 divisors, whose sum is σ = 20151882. Its totient is φ = 20151880.

The previous prime is 20151877. The next prime is 20151883. The reversal of 20151881 is 18815102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11055625 + 9096256 = 3325^2 + 3016^2 .

It is a cyclic number.

It is not a de Polignac number, because 20151881 - 2² = 20151877 is a prime.

It is a super-2 number, since 2×20151881² = 812196615676322, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 20151883, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20151881.

It is not a weakly prime, because it can be changed into another prime (20151883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10075940 + 10075941.

It is an arithmetic number, because the mean of its divisors is an integer number (10075941).

Almost surely, 2^20151881 is an apocalyptic number.

It is an amenable number.

20151881 is a deficient number, since it is larger than the sum of its proper divisors (1).

20151881 is an equidigital number, since it uses as much as digits as its factorization.

20151881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 20151881 is about 4489.0846505719. The cubic root of 20151881 is about 272.1271437377.

Adding to 20151881 its reverse (18815102), we get a palindrome (38966983).

The spelling of 20151881 in words is "twenty million, one hundred fifty-one thousand, eight hundred eighty-one".