81621481 has 8 divisors (see below), whose sum is σ = 84363264. Its totient is φ = 78886560.

The previous prime is 81621479. The next prime is 81621493. The reversal of 81621481 is 18412618.

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

It is a cyclic number.

It is not a de Polignac number, because 81621481 - 2¹ = 81621479 is a prime.

It is a super-2 number, since 2×81621481² = 13324132321266722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81621451) 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, 35880 + ... + 38086.

It is an arithmetic number, because the mean of its divisors is an integer number (10545408).

Almost surely, 2^81621481 is an apocalyptic number.

It is an amenable number.

81621481 is a deficient number, since it is larger than the sum of its proper divisors (2741783).

81621481 is a wasteful number, since it uses less digits than its factorization.

81621481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3431.

The product of its digits is 3072, while the sum is 31.

The square root of 81621481 is about 9034.4607476041. The cubic root of 81621481 is about 433.7786340920.

The spelling of 81621481 in words is "eighty-one million, six hundred twenty-one thousand, four hundred eighty-one".