21857801 has 16 divisors (see below), whose sum is σ = 26780544. Its totient is φ = 17412864.

The previous prime is 21857779. The next prime is 21857807. The reversal of 21857801 is 10875812.

It is a happy number.

It is not a de Polignac number, because 21857801 - 2¹⁸ = 21595657 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21857807) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8771 + ... + 10983.

It is an arithmetic number, because the mean of its divisors is an integer number (1673784).

Almost surely, 2^21857801 is an apocalyptic number.

It is an amenable number.

21857801 is a deficient number, since it is larger than the sum of its proper divisors (4922743).

21857801 is a wasteful number, since it uses less digits than its factorization.

21857801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2320.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21857801 is about 4675.2327214803. The cubic root of 21857801 is about 279.5989198029.

The spelling of 21857801 in words is "twenty-one million, eight hundred fifty-seven thousand, eight hundred one".