1988726021 has 6 divisors (see below), whose sum is σ = 2002006566. Its totient is φ = 1975533000.

The previous prime is 1988726017. The next prime is 1988726059. The reversal of 1988726021 is 1206278891.

It can be written as a sum of positive squares in only one way, i.e., 1984257025 + 4468996 = 44545^2 + 2114^2 .

It is not a de Polignac number, because 1988726021 - 2² = 1988726017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1988726081) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 20810 + ... + 66411.

It is an arithmetic number, because the mean of its divisors is an integer number (333667761).

Almost surely, 2^1988726021 is an apocalyptic number.

It is an amenable number.

1988726021 is a deficient number, since it is larger than the sum of its proper divisors (13280545).

1988726021 is an frugal number, since it uses more digits than its factorization.

1988726021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87523 (or 87372 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 44.

The square root of 1988726021 is about 44595.1344991805. The cubic root of 1988726021 is about 1257.5492003563.

The spelling of 1988726021 in words is "one billion, nine hundred eighty-eight million, seven hundred twenty-six thousand, twenty-one".