21506205145642 has 16 divisors (see below), whose sum is σ = 37652201107200. Its totient is φ = 9020839848048.

The previous prime is 21506205145591. The next prime is 21506205145703. The reversal of 21506205145642 is 24654150260512.

It is a happy 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, 16342100517 + ... + 16342101832.

It is an arithmetic number, because the mean of its divisors is an integer number (2353262569200).

Almost surely, 2^{21506205145642} is an apocalyptic number.

21506205145642 is a deficient number, since it is larger than the sum of its proper divisors (16145995961558).

21506205145642 is a wasteful number, since it uses less digits than its factorization.

21506205145642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32684202405.

The product of its (nonzero) digits is 576000, while the sum is 43.

The spelling of 21506205145642 in words is "twenty-one trillion, five hundred six billion, two hundred five million, one hundred forty-five thousand, six hundred forty-two".