390781981 has 4 divisors (see below), whose sum is σ = 390822592. Its totient is φ = 390741372.

The previous prime is 390781933. The next prime is 390781991. The reversal of 390781981 is 189187093.

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 a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 189187093 = 1223 ⋅154691.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-390781981 is a prime.

It is a super-2 number, since 2×390781981² = 305421113348568722, 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 (390781991) 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, 3196 + ... + 28138.

It is an arithmetic number, because the mean of its divisors is an integer number (97705648).

Almost surely, 2^390781981 is an apocalyptic number.

It is an amenable number.

390781981 is a deficient number, since it is larger than the sum of its proper divisors (40611).

390781981 is a wasteful number, since it uses less digits than its factorization.

390781981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40610.

The product of its (nonzero) digits is 108864, while the sum is 46.

The square root of 390781981 is about 19768.2063172155. The cubic root of 390781981 is about 731.1023446874.

The spelling of 390781981 in words is "three hundred ninety million, seven hundred eighty-one thousand, nine hundred eighty-one".