615981 has 4 divisors (see below), whose sum is σ = 821312. Its totient is φ = 410652.

The previous prime is 615971. The next prime is 615997. The reversal of 615981 is 189516.

It is a happy number.

615981 is digitally balanced in base 2 and base 7, because in such bases it contains all the possibile digits an equal number of times.

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 not a de Polignac number, because 615981 - 2⁵ = 615949 is a prime.

It is a super-2 number, since 2×615981² = 758865184722, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

615981 is strictly pandigital in base 7.

615981 is a lucky 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 615981.

It is not an unprimeable number, because it can be changed into a prime (615941) 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, 102661 + ... + 102666.

It is an arithmetic number, because the mean of its divisors is an integer number (205328).

2⁶¹⁵⁹⁸¹ is an apocalyptic number.

It is an amenable number.

615981 is a deficient number, since it is larger than the sum of its proper divisors (205331).

615981 is a wasteful number, since it uses less digits than its factorization.

615981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 205330.

The product of its digits is 2160, while the sum is 30.

The square root of 615981 is about 784.8445705998. The cubic root of 615981 is about 85.0855424871.

It can be divided in two parts, 615 and 981, that added together give a triangular number (1596 = T₅₆).

The spelling of 615981 in words is "six hundred fifteen thousand, nine hundred eighty-one".