1991420538 has 16 divisors (see below), whose sum is σ = 3993697920. Its totient is φ = 661997376.

The previous prime is 1991420461. The next prime is 1991420581. The reversal of 1991420538 is 8350241991.

It is a self number, because there is not a number n which added to its sum of digits gives 1991420538.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 449983 + ... + 454386.

It is an arithmetic number, because the mean of its divisors is an integer number (249606120).

Almost surely, 2^1991420538 is an apocalyptic number.

1991420538 is an abundant number, since it is smaller than the sum of its proper divisors (2002277382).

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

1991420538 is a wasteful number, since it uses less digits than its factorization.

1991420538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 904741.

The product of its (nonzero) digits is 77760, while the sum is 42.

The square root of 1991420538 is about 44625.3351584053. The cubic root of 1991420538 is about 1258.1168935201.

The spelling of 1991420538 in words is "one billion, nine hundred ninety-one million, four hundred twenty thousand, five hundred thirty-eight".