21621542540646 has 16 divisors (see below), whose sum is σ = 43256756660544. Its totient is φ = 7204902250344.

The previous prime is 21621542540641. The next prime is 21621542540669. The reversal of 21621542540646 is 64604524512612.

It is a super-2 number, since 2×21621542540646² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21621542540595 and 21621542540604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621542540641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 569628576 + ... + 569666531.

It is an arithmetic number, because the mean of its divisors is an integer number (2703547291284).

Almost surely, 2^{21621542540646} is an apocalyptic number.

21621542540646 is an abundant number, since it is smaller than the sum of its proper divisors (21635214119898).

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

21621542540646 is a wasteful number, since it uses less digits than its factorization.

21621542540646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1139298275.

The product of its (nonzero) digits is 2764800, while the sum is 48.

The spelling of 21621542540646 in words is "twenty-one trillion, six hundred twenty-one billion, five hundred forty-two million, five hundred forty thousand, six hundred forty-six".