21739901 has 4 divisors (see below), whose sum is σ = 21951072. Its totient is φ = 21528732.

The previous prime is 21739877. The next prime is 21739903. The reversal of 21739901 is 10993712.

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 21739901 - 2¹⁰ = 21738877 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21739903) 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, 105431 + ... + 105636.

It is an arithmetic number, because the mean of its divisors is an integer number (5487768).

Almost surely, 2^21739901 is an apocalyptic number.

It is an amenable number.

21739901 is a deficient number, since it is larger than the sum of its proper divisors (211171).

21739901 is a wasteful number, since it uses less digits than its factorization.

21739901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211170.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 21739901 is about 4662.6066743829. The cubic root of 21739901 is about 279.0952985259.

The spelling of 21739901 in words is "twenty-one million, seven hundred thirty-nine thousand, nine hundred one".