21533747437 has 4 divisors (see below), whose sum is σ = 21540771616. Its totient is φ = 21526723260.

The previous prime is 21533747419. The next prime is 21533747441. The reversal of 21533747437 is 73474733512.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21533747437 - 2¹⁵ = 21533714669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21533747467) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3507489 + ... + 3513622.

It is an arithmetic number, because the mean of its divisors is an integer number (5385192904).

Almost surely, 2^21533747437 is an apocalyptic number.

It is an amenable number.

21533747437 is a deficient number, since it is larger than the sum of its proper divisors (7024179).

21533747437 is an equidigital number, since it uses as much as digits as its factorization.

21533747437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7024178.

The product of its digits is 1481760, while the sum is 46.

The spelling of 21533747437 in words is "twenty-one billion, five hundred thirty-three million, seven hundred forty-seven thousand, four hundred thirty-seven".