21127491820 has 12 divisors (see below), whose sum is σ = 44367732864. Its totient is φ = 8450996720.

The previous prime is 21127491811. The next prime is 21127491851. The reversal of 21127491820 is 2819472112.

It is a self number, because there is not a number n which added to its sum of digits gives 21127491820.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 528187276 + ... + 528187315.

It is an arithmetic number, because the mean of its divisors is an integer number (3697311072).

Almost surely, 2^21127491820 is an apocalyptic number.

21127491820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21127491820 is an abundant number, since it is smaller than the sum of its proper divisors (23240241044).

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

21127491820 is a wasteful number, since it uses less digits than its factorization.

21127491820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1056374600 (or 1056374598 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 37.

The spelling of 21127491820 in words is "twenty-one billion, one hundred twenty-seven million, four hundred ninety-one thousand, eight hundred twenty".