60991981 has 4 divisors (see below), whose sum is σ = 61595964. Its totient is φ = 60388000.

The previous prime is 60991979. The next prime is 60991991. The reversal of 60991981 is 18919906.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18919906 = 2 ⋅9459953.

It can be written as a sum of positive squares in 2 ways, for example, as 54257956 + 6734025 = 7366^2 + 2595^2 .

It is a cyclic number.

It is not a de Polignac number, because 60991981 - 2¹ = 60991979 is a prime.

It is a super-2 number, since 2×60991981² = 7440043492608722, 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 (60991921) 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, 301840 + ... + 302041.

It is an arithmetic number, because the mean of its divisors is an integer number (15398991).

Almost surely, 2^60991981 is an apocalyptic number.

It is an amenable number.

60991981 is a deficient number, since it is larger than the sum of its proper divisors (603983).

60991981 is a wasteful number, since it uses less digits than its factorization.

60991981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 603982.

The product of its (nonzero) digits is 34992, while the sum is 43.

The square root of 60991981 is about 7809.7362951639. The cubic root of 60991981 is about 393.6324679527.

The spelling of 60991981 in words is "sixty million, nine hundred ninety-one thousand, nine hundred eighty-one".