21256645401 has 12 divisors (see below), whose sum is σ = 31841230512. Its totient is φ = 14171096772.

The previous prime is 21256645381. The next prime is 21256645477. The reversal of 21256645401 is 10454665212.

21256645401 is a `hidden beast` number, since 2 + 1 + 2 + 5 + 6 + 645 + 4 + 0 + 1 = 666.

It is not a de Polignac number, because 21256645401 - 2²² = 21252451097 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21256645481) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 43737711 + ... + 43738196.

It is an arithmetic number, because the mean of its divisors is an integer number (2653435876).

Almost surely, 2^21256645401 is an apocalyptic number.

It is an amenable number.

21256645401 is a deficient number, since it is larger than the sum of its proper divisors (10584585111).

21256645401 is an frugal number, since it uses more digits than its factorization.

21256645401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87475922 (or 87475910 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 36.

The spelling of 21256645401 in words is "twenty-one billion, two hundred fifty-six million, six hundred forty-five thousand, four hundred one".