81521377 has 8 divisors (see below), whose sum is σ = 93505856. Its totient is φ = 69621552.

The previous prime is 81521371. The next prime is 81521387. The reversal of 81521377 is 77312518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81521377 - 2³ = 81521369 is a prime.

It is a super-2 number, since 2×81521377² = 13291469815952258, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81521371) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19083 + ... + 22960.

It is an arithmetic number, because the mean of its divisors is an integer number (11688232).

Almost surely, 2^81521377 is an apocalyptic number.

It is an amenable number.

81521377 is a deficient number, since it is larger than the sum of its proper divisors (11984479).

81521377 is a wasteful number, since it uses less digits than its factorization.

81521377 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42327.

The product of its digits is 11760, while the sum is 34.

The square root of 81521377 is about 9028.9189275350. The cubic root of 81521377 is about 433.6012267891.

The spelling of 81521377 in words is "eighty-one million, five hundred twenty-one thousand, three hundred seventy-seven".