72961981 has 4 divisors (see below), whose sum is σ = 73211292. Its totient is φ = 72712672.

The previous prime is 72961969. The next prime is 72961991. The reversal of 72961981 is 18916927.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18916927 = 139 ⋅136093.

It can be written as a sum of positive squares in 2 ways, for example, as 71825625 + 1136356 = 8475^2 + 1066^2 .

It is a cyclic number.

It is not a de Polignac number, because 72961981 - 2¹³ = 72953789 is a prime.

It is a super-2 number, since 2×72961981² = 10646901342888722, 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 (72961921) 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, 124216 + ... + 124801.

It is an arithmetic number, because the mean of its divisors is an integer number (18302823).

Almost surely, 2^72961981 is an apocalyptic number.

It is an amenable number.

72961981 is a deficient number, since it is larger than the sum of its proper divisors (249311).

72961981 is a wasteful number, since it uses less digits than its factorization.

72961981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249310.

The product of its digits is 54432, while the sum is 43.

The square root of 72961981 is about 8541.7785618687. The cubic root of 72961981 is about 417.8613525653.

It can be divided in two parts, 7296 and 1981, that multiplied together give a triangular number (14453376 = T₅₃₇₆).

The spelling of 72961981 in words is "seventy-two million, nine hundred sixty-one thousand, nine hundred eighty-one".