21397156536 has 384 divisors, whose sum is σ = 68369356800. Its totient is φ = 5547709440.

The previous prime is 21397156531. The next prime is 21397156553. The reversal of 21397156536 is 63565179312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21397156531) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 39117015 + ... + 39117561.

It is an arithmetic number, because the mean of its divisors is an integer number (178045200).

Almost surely, 2^21397156536 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21397156536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34184678400).

21397156536 is an abundant number, since it is smaller than the sum of its proper divisors (46972200264).

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

21397156536 is a wasteful number, since it uses less digits than its factorization.

21397156536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 667 (or 656 counting only the distinct ones).

The product of its digits is 1020600, while the sum is 48.

The spelling of 21397156536 in words is "twenty-one billion, three hundred ninety-seven million, one hundred fifty-six thousand, five hundred thirty-six".