78191820 has 72 divisors (see below), whose sum is σ = 271069344. Its totient is φ = 17872128.

The previous prime is 78191807. The next prime is 78191831. The reversal of 78191820 is 2819187.

It is a super-2 number, since 2×78191820² = 12227921429824800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 29769 + ... + 32288.

It is an arithmetic number, because the mean of its divisors is an integer number (3764852).

Almost surely, 2^78191820 is an apocalyptic number.

78191820 is a gapful number since it is divisible by the number (70) formed by its first and last digit.

It is an amenable number.

78191820 is an abundant number, since it is smaller than the sum of its proper divisors (192877524).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

78191820 is a wasteful number, since it uses less digits than its factorization.

78191820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62079 (or 62074 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 78191820 is about 8842.6138669513. The cubic root of 78191820 is about 427.6158299040.

The spelling of 78191820 in words is "seventy-eight million, one hundred ninety-one thousand, eight hundred twenty".