81898639 has 16 divisors (see below), whose sum is σ = 90184320. Its totient is φ = 74027520.

The previous prime is 81898633. The next prime is 81898669. The reversal of 81898639 is 93689818.

81898639 = T₂₅₆ + T₂₅₇ + ... + T₇₉₇.

It is not a de Polignac number, because 81898639 - 2⁷ = 81898511 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81898633) 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, 133297 + ... + 133909.

It is an arithmetic number, because the mean of its divisors is an integer number (5636520).

Almost surely, 2^81898639 is an apocalyptic number.

81898639 is a deficient number, since it is larger than the sum of its proper divisors (8285681).

81898639 is a wasteful number, since it uses less digits than its factorization.

81898639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 930.

The product of its digits is 746496, while the sum is 52.

The square root of 81898639 is about 9049.7866825688. The cubic root of 81898639 is about 434.2690662364.

It can be divided in two parts, 818986 and 39, that added together give a square (819025 = 905²).

The spelling of 81898639 in words is "eighty-one million, eight hundred ninety-eight thousand, six hundred thirty-nine".