21001202780 has 48 divisors (see below), whose sum is σ = 44309069280. Its totient is φ = 8361216768.

The previous prime is 21001202771. The next prime is 21001202839. The reversal of 21001202780 is 8720210012.

It is a congruent number.

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, 5969582 + ... + 5973098.

It is an arithmetic number, because the mean of its divisors is an integer number (923105610).

Almost surely, 2^21001202780 is an apocalyptic number.

21001202780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001202780 is an abundant number, since it is smaller than the sum of its proper divisors (23307866500).

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

21001202780 is a wasteful number, since it uses less digits than its factorization.

21001202780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4838 (or 4836 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 23.

Adding to 21001202780 its reverse (8720210012), we get a palindrome (29721412792).

The spelling of 21001202780 in words is "twenty-one billion, one million, two hundred two thousand, seven hundred eighty".