81377621 has 4 divisors (see below), whose sum is σ = 87637452. Its totient is φ = 75117792.

The previous prime is 81377617. The next prime is 81377641. The reversal of 81377621 is 12677318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4622500 + 76755121 = 2150^2 + 8761^2 .

It is a cyclic number.

It is not a de Polignac number, because 81377621 - 2² = 81377617 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81377641) 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, 3129896 + ... + 3129921.

It is an arithmetic number, because the mean of its divisors is an integer number (21909363).

Almost surely, 2^81377621 is an apocalyptic number.

It is an amenable number.

81377621 is a deficient number, since it is larger than the sum of its proper divisors (6259831).

81377621 is a wasteful number, since it uses less digits than its factorization.

81377621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6259830.

The product of its digits is 14112, while the sum is 35.

The square root of 81377621 is about 9020.9545503788. The cubic root of 81377621 is about 433.3462038912.

The spelling of 81377621 in words is "eighty-one million, three hundred seventy-seven thousand, six hundred twenty-one".