21661369866 has 32 divisors (see below), whose sum is σ = 48148531200. Its totient is φ = 7218633600.

The previous prime is 21661369853. The next prime is 21661369879. The reversal of 21661369866 is 66896316612.

21661369866 is a `hidden beast` number, since 2 + 16 + 613 + 6 + 9 + 8 + 6 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (21661369853) and next prime (21661369879).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 174391 + ... + 271541.

It is an arithmetic number, because the mean of its divisors is an integer number (1504641600).

Almost surely, 2^21661369866 is an apocalyptic number.

21661369866 is an abundant number, since it is smaller than the sum of its proper divisors (26487161334).

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

21661369866 is a wasteful number, since it uses less digits than its factorization.

21661369866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101291 (or 101285 counting only the distinct ones).

The product of its digits is 3359232, while the sum is 54.

The spelling of 21661369866 in words is "twenty-one billion, six hundred sixty-one million, three hundred sixty-nine thousand, eight hundred sixty-six".