21506137406544 has 40 divisors (see below), whose sum is σ = 63494310439360. Its totient is φ = 6144610687488.

The previous prime is 21506137406527. The next prime is 21506137406561. The reversal of 21506137406544 is 44560473160512.

It is an interprime number because it is at equal distance from previous prime (21506137406527) and next prime (21506137406561).

It is a super-2 number, since 2×21506137406544² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a junction number, because it is equal to n+sod(n) for n = 21506137406493 and 21506137406502.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32003180329 + ... + 32003181000.

It is an arithmetic number, because the mean of its divisors is an integer number (1587357760984).

Almost surely, 2^{21506137406544} is an apocalyptic number.

21506137406544 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21506137406544 is an abundant number, since it is smaller than the sum of its proper divisors (41988173032816).

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

21506137406544 is a wasteful number, since it uses less digits than its factorization.

21506137406544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64006361347 (or 64006361341 counting only the distinct ones).

The product of its (nonzero) digits is 2419200, while the sum is 48.

The spelling of 21506137406544 in words is "twenty-one trillion, five hundred six billion, one hundred thirty-seven million, four hundred six thousand, five hundred forty-four".