21437081687 has 12 divisors (see below), whose sum is σ = 25467590880. Its totient is φ = 17983689696.

The previous prime is 21437081629. The next prime is 21437081689. The reversal of 21437081687 is 78618073412.

It is a happy number.

It is not a de Polignac number, because 21437081687 - 2²⁸ = 21168646231 is a prime.

It is a super-2 number, since 2×21437081687² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (47).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21437081689) 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, 4651862 + ... + 4656467.

It is an arithmetic number, because the mean of its divisors is an integer number (2122299240).

Almost surely, 2^21437081687 is an apocalyptic number.

21437081687 is a deficient number, since it is larger than the sum of its proper divisors (4030509193).

21437081687 is an equidigital number, since it uses as much as digits as its factorization.

21437081687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9308390 (or 9308383 counting only the distinct ones).

The product of its (nonzero) digits is 451584, while the sum is 47.

The spelling of 21437081687 in words is "twenty-one billion, four hundred thirty-seven million, eighty-one thousand, six hundred eighty-seven".