21661354546 has 16 divisors (see below), whose sum is σ = 34995605400. Its totient is φ = 9996352128.

The previous prime is 21661354541. The next prime is 21661354657. The reversal of 21661354546 is 64545316612.

It can be written as a sum of positive squares in 4 ways, for example, as 12850716321 + 8810638225 = 113361^2 + 93865^2 .

It is a super-2 number, since 2×21661354546² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21661354541) 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, 194200 + ... + 284668.

Almost surely, 2^21661354546 is an apocalyptic number.

21661354546 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21661354546 is a deficient number, since it is larger than the sum of its proper divisors (13334250854).

21661354546 is a wasteful number, since it uses less digits than its factorization.

21661354546 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99693.

The product of its digits is 518400, while the sum is 43.

The spelling of 21661354546 in words is "twenty-one billion, six hundred sixty-one million, three hundred fifty-four thousand, five hundred forty-six".