21501601 has 4 divisors (see below), whose sum is σ = 23456304. Its totient is φ = 19546900.

The previous prime is 21501593. The next prime is 21501643. The reversal of 21501601 is 10610512.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21501601 - 2³ = 21501593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21501661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 977335 + ... + 977356.

It is an arithmetic number, because the mean of its divisors is an integer number (5864076).

Almost surely, 2^21501601 is an apocalyptic number.

It is an amenable number.

21501601 is a deficient number, since it is larger than the sum of its proper divisors (1954703).

21501601 is a wasteful number, since it uses less digits than its factorization.

21501601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1954702.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 21501601 is about 4636.9818848040. The cubic root of 21501601 is about 278.0717901995.

The spelling of 21501601 in words is "twenty-one million, five hundred one thousand, six hundred one".