21002778500 has 48 divisors (see below), whose sum is σ = 50040087552. Its totient is φ = 7637372000.

The previous prime is 21002778479. The next prime is 21002778539. The reversal of 21002778500 is 587720012.

It is a super-2 number, since 2×21002778500² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1903844 + ... + 1914843.

It is an arithmetic number, because the mean of its divisors is an integer number (1042501824).

Almost surely, 2^21002778500 is an apocalyptic number.

21002778500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21002778500 is an abundant number, since it is smaller than the sum of its proper divisors (29037309052).

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

21002778500 is a wasteful number, since it uses less digits than its factorization.

21002778500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3818717 (or 3818705 counting only the distinct ones).

The product of its (nonzero) digits is 7840, while the sum is 32.

The spelling of 21002778500 in words is "twenty-one billion, two million, seven hundred seventy-eight thousand, five hundred".