81901551 has 16 divisors (see below), whose sum is σ = 114428160. Its totient is φ = 52008000.

The previous prime is 81901507. The next prime is 81901577. The reversal of 81901551 is 15510918.

It is not a de Polignac number, because 81901551 - 2¹⁰ = 81900527 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81900551) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14955 + ... + 19683.

It is an arithmetic number, because the mean of its divisors is an integer number (7151760).

Almost surely, 2^81901551 is an apocalyptic number.

81901551 is a deficient number, since it is larger than the sum of its proper divisors (32526609).

81901551 is a wasteful number, since it uses less digits than its factorization.

81901551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5006.

The product of its (nonzero) digits is 1800, while the sum is 30.

The square root of 81901551 is about 9049.9475689089. The cubic root of 81901551 is about 434.2742131536.

The spelling of 81901551 in words is "eighty-one million, nine hundred one thousand, five hundred fifty-one".