151781 has 4 divisors (see below), whose sum is σ = 173472. Its totient is φ = 130092.

The previous prime is 151771. The next prime is 151783. The reversal of 151781 is 187151.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 151781 - 2⁶ = 151717 is a prime.

It is a super-2 number, since 2×151781² = 46074943922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 151781.

It is not an unprimeable number, because it can be changed into a prime (151783) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10835 + ... + 10848.

It is an arithmetic number, because the mean of its divisors is an integer number (43368).

2¹⁵¹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

151781 is a deficient number, since it is larger than the sum of its proper divisors (21691).

151781 is an equidigital number, since it uses as much as digits as its factorization.

151781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21690.

The product of its digits is 280, while the sum is 23.

The square root of 151781 is about 389.5908109799. The cubic root of 151781 is about 53.3423899550.

The spelling of 151781 in words is "one hundred fifty-one thousand, seven hundred eighty-one".