261506021 has 16 divisors (see below), whose sum is σ = 322617600. Its totient is φ = 207005568.

The previous prime is 261506017. The next prime is 261506027. The reversal of 261506021 is 120605162.

It is not a de Polignac number, because 261506021 - 2² = 261506017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261506027) 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, 23336 + ... + 32673.

It is an arithmetic number, because the mean of its divisors is an integer number (20163600).

Almost surely, 2^261506021 is an apocalyptic number.

It is an amenable number.

261506021 is a deficient number, since it is larger than the sum of its proper divisors (61111579).

261506021 is a wasteful number, since it uses less digits than its factorization.

261506021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56068.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 261506021 is about 16171.1477947609. The cubic root of 261506021 is about 639.4803896077.

The spelling of 261506021 in words is "two hundred sixty-one million, five hundred six thousand, twenty-one".