21661602425 has 12 divisors (see below), whose sum is σ = 26872781520. Its totient is φ = 17321285520.

The previous prime is 21661602401. The next prime is 21661602437. The reversal of 21661602425 is 52420616612.

It is not a de Polignac number, because 21661602425 - 2¹⁴ = 21661586041 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 144347 + ... + 253296.

It is an arithmetic number, because the mean of its divisors is an integer number (2239398460).

Almost surely, 2^21661602425 is an apocalyptic number.

21661602425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21661602425 is a deficient number, since it is larger than the sum of its proper divisors (5211179095).

21661602425 is a wasteful number, since it uses less digits than its factorization.

21661602425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399832 (or 399827 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 35.

The spelling of 21661602425 in words is "twenty-one billion, six hundred sixty-one million, six hundred two thousand, four hundred twenty-five".