21697421971 has 2 divisors, whose sum is σ = 21697421972. Its totient is φ = 21697421970.

The previous prime is 21697421957. The next prime is 21697421989. The reversal of 21697421971 is 17912479612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21697421971 - 2⁵ = 21697421939 is a prime.

It is not a weakly prime, because it can be changed into another prime (21697421071) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10848710985 + 10848710986.

It is an arithmetic number, because the mean of its divisors is an integer number (10848710986).

Almost surely, 2^21697421971 is an apocalyptic number.

21697421971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21697421971 is an equidigital number, since it uses as much as digits as its factorization.

21697421971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 381024, while the sum is 49.

The spelling of 21697421971 in words is "twenty-one billion, six hundred ninety-seven million, four hundred twenty-one thousand, nine hundred seventy-one".