21012778437 has 12 divisors (see below), whose sum is σ = 32591248416. Its totient is φ = 12007301880.

The previous prime is 21012778417. The next prime is 21012778463. The reversal of 21012778437 is 73487721012.

It is not a de Polignac number, because 21012778437 - 2¹⁰ = 21012777413 is a prime.

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012778417) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 71471889 + ... + 71472182.

It is an arithmetic number, because the mean of its divisors is an integer number (2715937368).

Almost surely, 2^21012778437 is an apocalyptic number.

It is an amenable number.

21012778437 is a deficient number, since it is larger than the sum of its proper divisors (11578469979).

21012778437 is a wasteful number, since it uses less digits than its factorization.

21012778437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142944088 (or 142944081 counting only the distinct ones).

The product of its (nonzero) digits is 131712, while the sum is 42.

The spelling of 21012778437 in words is "twenty-one billion, twelve million, seven hundred seventy-eight thousand, four hundred thirty-seven".