21697421958 has 24 divisors (see below), whose sum is σ = 47036280096. Its totient is φ = 7228597200.

The previous prime is 21697421957. The next prime is 21697421971. The reversal of 21697421958 is 85912479612.

It is a happy number.

21697421958 is a `hidden beast` number, since 2 + 169 + 7 + 421 + 9 + 58 = 666.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21697421957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 288453 + ... + 355808.

It is an arithmetic number, because the mean of its divisors is an integer number (1959845004).

Almost surely, 2^21697421958 is an apocalyptic number.

21697421958 is an abundant number, since it is smaller than the sum of its proper divisors (25338858138).

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

21697421958 is a wasteful number, since it uses less digits than its factorization.

21697421958 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 646140 (or 646137 counting only the distinct ones).

The product of its digits is 2177280, while the sum is 54.

The spelling of 21697421958 in words is "twenty-one billion, six hundred ninety-seven million, four hundred twenty-one thousand, nine hundred fifty-eight".