145921981 has 4 divisors (see below), whose sum is σ = 149026752. Its totient is φ = 142817212.

The previous prime is 145921973. The next prime is 145921987. The reversal of 145921981 is 189129541.

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, and also an emirpimes, since its reverse is a distinct semiprime: 189129541 = 439 ⋅430819.

It is a cyclic number.

It is not a de Polignac number, because 145921981 - 2³ = 145921973 is a prime.

It is a super-2 number, since 2×145921981² = 42586449077928722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (145921987) 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, 1552315 + ... + 1552408.

It is an arithmetic number, because the mean of its divisors is an integer number (37256688).

Almost surely, 2^145921981 is an apocalyptic number.

It is an amenable number.

145921981 is a deficient number, since it is larger than the sum of its proper divisors (3104771).

145921981 is an equidigital number, since it uses as much as digits as its factorization.

145921981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3104770.

The product of its digits is 25920, while the sum is 40.

The square root of 145921981 is about 12079.8170929861. The cubic root of 145921981 is about 526.4699316377.

The spelling of 145921981 in words is "one hundred forty-five million, nine hundred twenty-one thousand, nine hundred eighty-one".