81261536 has 12 divisors (see below), whose sum is σ = 159983712. Its totient is φ = 40630752.

The previous prime is 81261517. The next prime is 81261563. The reversal of 81261536 is 63516218.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (32), and also a Moran number because the ratio is a prime number: 2539423 = 81261536 / (8 + 1 + 2 + 6 + 1 + 5 + 3 + 6).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1269680 + ... + 1269743.

It is an arithmetic number, because the mean of its divisors is an integer number (13331976).

Almost surely, 2^81261536 is an apocalyptic number.

It is an amenable number.

81261536 is a deficient number, since it is larger than the sum of its proper divisors (78722176).

81261536 is a wasteful number, since it uses less digits than its factorization.

81261536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2539433 (or 2539425 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 81261536 is about 9014.5180680944. The cubic root of 81261536 is about 433.1400500272.

The spelling of 81261536 in words is "eighty-one million, two hundred sixty-one thousand, five hundred thirty-six".