21878497537 has 16 divisors (see below), whose sum is σ = 23936126032. Its totient is φ = 19876700160.

The previous prime is 21878497507. The next prime is 21878497559. The reversal of 21878497537 is 73579487812.

It can be written as a sum of positive squares in 8 ways, for example, as 11360149056 + 10518348481 = 106584^2 + 102559^2 .

It is a cyclic number.

It is not a de Polignac number, because 21878497537 - 2⁷ = 21878497409 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21878497507) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 180313 + ... + 276169.

It is an arithmetic number, because the mean of its divisors is an integer number (1496007877).

Almost surely, 2^21878497537 is an apocalyptic number.

It is an amenable number.

21878497537 is a deficient number, since it is larger than the sum of its proper divisors (2057628495).

21878497537 is a wasteful number, since it uses less digits than its factorization.

21878497537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96148.

The product of its digits is 23708160, while the sum is 61.

The spelling of 21878497537 in words is "twenty-one billion, eight hundred seventy-eight million, four hundred ninety-seven thousand, five hundred thirty-seven".