81621501 has 8 divisors (see below), whose sum is σ = 117200160. Its totient is φ = 50228592.

The previous prime is 81621497. The next prime is 81621509. The reversal of 81621501 is 10512618.

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

It is not a de Polignac number, because 81621501 - 2² = 81621497 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81621509) 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, 1046391 + ... + 1046468.

It is an arithmetic number, because the mean of its divisors is an integer number (14650020).

Almost surely, 2^81621501 is an apocalyptic number.

It is an amenable number.

81621501 is a deficient number, since it is larger than the sum of its proper divisors (35578659).

81621501 is a wasteful number, since it uses less digits than its factorization.

81621501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2092875.

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 81621501 is about 9034.4618544770. The cubic root of 81621501 is about 433.7786695221.

The spelling of 81621501 in words is "eighty-one million, six hundred twenty-one thousand, five hundred one".