81953919 has 12 divisors (see below), whose sum is σ = 118491256. Its totient is φ = 54583632.

The previous prime is 81953909. The next prime is 81953929. The reversal of 81953919 is 91935918.

It is an interprime number because it is at equal distance from previous prime (81953909) and next prime (81953929).

It is not a de Polignac number, because 81953919 - 2⁵ = 81953887 is a prime.

It is a super-2 number, since 2×81953919² = 13432889678917122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81953909) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7164 + ... + 14670.

Almost surely, 2^81953919 is an apocalyptic number.

81953919 is a deficient number, since it is larger than the sum of its proper divisors (36537337).

81953919 is a wasteful number, since it uses less digits than its factorization.

81953919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8726 (or 8723 counting only the distinct ones).

The product of its digits is 87480, while the sum is 45.

The square root of 81953919 is about 9052.8403829958. The cubic root of 81953919 is about 434.3667520060.

The spelling of 81953919 in words is "eighty-one million, nine hundred fifty-three thousand, nine hundred nineteen".