21055543646 has 16 divisors (see below), whose sum is σ = 31749637920. Its totient is φ = 10472474880.

The previous prime is 21055543627. The next prime is 21055543657. The reversal of 21055543646 is 64634555012.

It is a happy number.

It is a super-2 number, since 2×21055543646² (a number of 21 digits) contains 22 as substring.

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, 260306 + ... + 331466.

It is an arithmetic number, because the mean of its divisors is an integer number (1984352370).

Almost surely, 2^21055543646 is an apocalyptic number.

21055543646 is a deficient number, since it is larger than the sum of its proper divisors (10694094274).

21055543646 is a wasteful number, since it uses less digits than its factorization.

21055543646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71939.

The product of its (nonzero) digits is 432000, while the sum is 41.

The spelling of 21055543646 in words is "twenty-one billion, fifty-five million, five hundred forty-three thousand, six hundred forty-six".